Apple Muffins with Browned Butter Oat Streusel

During my internship at America’s Test Kitchen, we were challenged to create a superb muffin recipe and write a Cook’s Illustrated-style piece about it. Here’s mine!

Streusel-topped apple muffins


In the winter of 2018-2019, I moved cross-country to complete an internship at America’s Test Kitchen. As a final project, we were challenged to develop a muffin recipe and write a short article in the style of Cook’s Illustrated. Here’s mine!

Mastering “Coffee Shop” Muffins

Imagine this: a cool Sunday morning at a cafe, sipping a cup of your favorite tea or coffee. If you’re like me, you also have a muffin on the table—the kind that is piled high with streusel and filled with bits of fruit. Modern coffee shop-style muffins are wonderful things, but can often be excessive: dessert-like sweetness, cake-like fluffiness, and big enough to serve two (or three!).

I decided to bring the classic apple streusel muffin into the kitchen and make a pastry that’s both easy to whip up and worthy of your Sunday morning at home. To do so, I paid key attention to the texture, sweetness, streusel, and the all-important apple.

A Talk About Texture

What sets muffins and cupcakes apart (besides frosting, of course) is the texture or crumb. A good cupcake is light and airy on the inside, whereas muffins tend to have a tighter crumb. This distinction is accomplished largely through mixing. Cakes are often made using the creaming method, which works by beating butter and sugar together to create microscopic pockets of air in the batter, yielding a fluffy crumb.

By using the aptly named muffin method—whisking dry and wet ingredients separately, then gently stirring together—I ensured a muffin with a satisfying bite, fitting for a breakfast pastry. The batter is best when kept a little lumpy. By not mixing the batter until completely smooth, the gluten development is limited, thus guarding the muffins against getting tough or chewy.

Because this method uses a liquid fat—here, melted butter—it is important to make sure all the ingredients for the batter are at room temperature. If the eggs or yogurt are chilled from the refrigerator, they can re-solidify the butter and prevent the batter from fully hydrating.

Speaking of yogurt*, it also plays a key role in texture. It is a great option to create moist baked goods because it is made up of an emulsion of protein, water, and fat. Keeping the water bound with these other molecules helps to prevent drying out during baking, while the fat (even in low-fat yogurt) tenderizes and further adds moisture to the batter.

Lastly, yogurt also adds acidity which provides a trigger for the baking powder to provide the “lift” for these muffins, as well as a subtle tang to balance sweetness.

Sorting Out Sweetness

Another important distinction between cake and muffins is the ratio of sugar with other ingredients. I avoided an overly sweet muffin to let other flavors shine—and prevent the feeling of an impending 10 AM sugar crash. To do this, I kept the total amount of sugar below one cup in the batter and used both granulated and dark brown sugar. The extra molasses in dark brown sugar adds subtle notes of caramel and rounds out the saccharine edge. It keeps the muffins moist after baking through its hygroscopic characteristics (the tendency of sugar to attract and absorb moisture from the surrounding air).

By taking a few extra minutes to brown the butter, the muffins gain nuttiness that is complemented by the warm spice flavor of cinnamon and nutmeg. This adds comforting complexity to the autumnal flavors. Less sugar in the batter leaves the opportunity to have a sweeter “pop” of apple and more of everyone’s favorite part of the muffin: the streusel.

The Struggle for Streusel

Whereas many coffee shop-style muffins have a sandy crumble, I wanted to provide this version with a crisp bite and toffee-like flavor. The comforting taste, reminiscent of warm oatmeal cookies, came naturally with the combination of browned butter, brown sugar, and old-fashioned oats. Surprisingly, achieving the crunch in the clusters of streusel is what proved to be the challenge.

I tried various ratios of butter, flour, and sugar but none hit the mark. Streusel that formed moist clumps when mixed ended up with the butter melting down the sides of the muffin during baking and caused greasy bottoms. Streusel that had enough flour to fully soak up the butter ended up powdery and loose. The—seemingly counterintuitive—solution to a crunchy topping? Add water.

Adding the melted browned butter to the mixture first helps to coat the gluten strands in the flour and keep the streusel chewy on the inside, while stirring in water at the end allows for the formation of clumps that retained their shape throughout baking. A period of chilling allows the mixture to fully hydrate and further create distinct morsels. During cooking, the water in the mixture steams and evaporates, leaving a crispy streusel.

One last obstacle was the issue of how to build beautiful piles of crumble on top of each muffin—without having most of it end up on the flats of the muffin tin. By folding squares of parchment into muffin liners with tall, “lotus-style” sides, it allowed the muffins to bake tall and still hold a generous pinch of delicious streusel.

An Assortment of Apples

Even with all the talk of texture and streusel, the real star of these muffins are the apples. I tried five different sweet varieties: Gala, Golden Delicious, Cripps Pink, Braeburn, and dried apples.

After baking, diced Golden Delicious apples seemed to “melt” into the muffin. They exhibited a very soft texture and lackluster fruit flavor. Galas retained a decently firm texture, but again lost much of their flavor. Small pieces of dried apples completely absorbed moisture from the batter and caused the baked muffin to be chewy and dry. Braeburn and Cripps Pink apples were the clear winners, as they both provided pleasant bursts of sweet, ripe apple flavor while maintaining structural integrity. The Braeburn variety just edged out Cripps Pink with its superior apple flavor.

Even after all the testing, these muffins still had one more surprise in store for me: how incredible they were the next day. The harmony of browned butter, warm spice, and sweet apple develops even more overnight. So make your Sunday batch, but make sure to save one (or two) for Monday morning.

  • apple muffins with dry, straggly streusel on top
  • apple muffins with spotty, melty streusel
  • a test batch of apple muffins, one without liners and with lotus-style liners
  • apple muffins with brown butter oat streusel in tall muffin liners in the tin

The slideshow includes a couple of shots from the development process. From my first batch, through streusel struggles, to the final muffin!

Apple Muffins with Browned Butter Oat Streusel

Active Time25 minutes
Cook Time30 minutes
Total Time55 minutes
Yield12 muffins


Crisp, sweet apples work best in these muffins. In tests, the Braeburn variety yielded the preferred soft-but-distinct texture and fruity apple flavor, but Cripps Pink apples (also called Pink Lady apples) are a good option as well. This recipe uses parchment squares to create tall muffin liners; they allow for the muffins to maintain height while baking and hold generous piles of streusel. Alternatively, lotus-style muffin liners can be purchased and used.
*UPDATE 7/2/2020: This recipe also works when substituting buttermilk or acidulated milk (whole or 2% milk + a splash of white vinegar) for yogurt.


Brown Butter Oat Streusel

  • 90 grams all-purpose flour (¾ cup)
  • 67 grams old-fashioned oats (¾ cup)
  • 99 grams dark brown sugar (½ cup)
  • ¼ tsp. table salt
  • 198 grams unsalted butter (14 Tbsp.)
  • 2 Tbsp. water
  • 1 ½ tsp. vanilla extract

Apple Muffins

  • 240 grams all-purpose flour (2 cups)
  • 2 tsp. ground cinnamon
  • 2 tsp. baking powder
  • ¾ tsp. baking soda
  • ¼ tsp. ground nutmeg
  • ¼ tsp. table salt
  • 2 large eggs room temperature
  • 1 cup plain low-fat yogurt room temperature*
  • 99 grams granulated sugar (½ cup)
  • 50 grams dark brown sugar (¼ cup)
  • 1 tsp. vanilla extract
  • 12 ounces Braeburn apples , peeled, cored, and cut into ¼-inch pieces (1 ½ cups diced pieces)



  • Adjust oven rack to middle position and heat oven to 350℉. Cut 12 6-inch squares out of parchment paper. Gently press and crease paper squares into a standard 12-cup muffin tin to create muffin liners with tall, folded walls. Paper may not fully stay in cups until they are filled with muffin batter.


  • 90 grams all-purpose flour
    67 grams old-fashioned oats
    99 grams dark brown sugar
    ¼ tsp. table salt
    Stir flour, oats, sugar, and salt together in medium bowl.
  • 198 grams unsalted butter
    Melt butter in small saucepan over medium-high heat. Continue to cook, stirring frequently, until butter is lightly browned and aromatic, 2 to 3 minutes. Reserve ½ cup butter for muffin mixture and set aside to cool.
  • 2 Tbsp. water
    1 ½ tsp. vanilla extract
    Stir remaining browned butter (should be about 6 tablespoons) into flour mixture until evenly combined. Add water and vanilla extract and stir until evenly moistened and mixture starts to clump. Chill mixture for at least 10 minutes, or until ready to use.


  • 240 grams all-purpose flour
    2 tsp. ground cinnamon
    2 tsp. baking powder
    ¾ tsp. baking soda
    ¼ tsp. ground nutmeg
    ¼ tsp. table salt
    Whisk flour, cinnamon, baking powder, baking soda, nutmeg, and salt together in a large bowl.
  • 2 large eggs
    1 cup plain low-fat yogurt
    99 grams granulated sugar
    50 grams dark brown sugar
    1 tsp. vanilla extract
    12 ounces Braeburn apples
    In a separate medium bowl, whisk eggs, yogurt, granulated sugar, brown sugar, and vanilla extract until no lumps of brown sugar remain. Stir in reserved browned butter until smooth, then fold in diced apples.
  • Add egg mixture to flour mixture and use a rubber spatula to gently mix, just until no visible flour remains. Batter should be thick and slightly lumpy. Use a level ⅓-cup dry measurement to fill each prepared muffin cup. Use your hands to break apart streusel mixture and crumble evenly over each muffin, breaking up any clumps larger than a marble. Bake until a toothpick inserted into the center of the muffins comes out clean, about 25 to 30 minutes, rotating muffin tin halfway through baking.
  • Let cool in tin for at least 20 minutes. Cooled muffins can be stored in an airtight container or zipper lock bag at room temperature for up to 3 days.

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