Add dry ingredients and apples, stirring just until combined using a rubber spatula. If you still see small streaks of flour that's okay.
Scoop batter into prepared muffin tin. The cavities will be almost full. Allow to rest while you make the streusel topping.
In a small mixing bowl, combine the streusel ingredients. I like to use my fingers to squeeze the ingredients until they come together and are completely combined. Once you can squeeze it in your hands and it mostly holds its shape, it’s ready!
2.1 ounces all purpose flour, 1.8 ounces brown sugar, 1/2 teaspoon ground cinnamon, pinch of salt, 3 Tablespoons unsalted butter
Sprinkle tops of each muffin generously with streusel topping, gently pressing down on the tops to ensure that it sticks. Each cup should be full once the streusel is added.
Bake muffins at 425 F for 5 minutes. Then reduce the temperature to 350 F and bake another for 13-18 minutes, or until a toothpick inserted in the center comes out clean. Ours were done in 17 minutes.TIP - Be sure to perform the toothpick test on more than one muffin. One might seem done while the rest aren’t! I usually check at least one in front and one in the back, but often times I’ll check three. If they aren’t done, they will sink in the middle.
Cool for 5 minutes in the pan, then remove from pan to a wire rack to cool completely.
When cooled, line the work surface with waxed paper and place the wire rack of muffins over it. Mix together glaze ingredients.
Don’t use a mixer for this recipe. Whisking and stirring by hand is all that’s needed, and using a mixer can beat too much air into the batter. It can also activate the gluten, which can result in muffins that are tough and dense. It can also cause your muffins to rise unevenly.
For the streusel I mention using chilled or room temperature butter. Both will work. I like to remove the butter from the fridge and cut it into squares about 15 minutes before I make the streusel.
For this recipe I used whole milk as it adds to the richness, flavor, and moist texture of these muffins. I have also made these with 2% milk with great results. You can use lower fat milks, but it may affect the moisture of the muffins.
We used 2 (5-oz) Honeycrisp apples, which yielded 2 cups of peeled and chopped apples. Other suitable apples are Braeburn, Pink Lady, Jonagold, Fuji, and Granny Smith. Any apple known for its firm texture and crisp skin. It’s best to avoid softer apples like Red Delicious and McIntosh which could become mushy when baking.