1-Start by preheating your oven to 425°F (220°C) and prepare your muffin pans with nonstick spray or liners to set the stage for baking. This high initial heat helps the muffins rise tall and develop that signature crumb topping.

2-Next, mix the crumb topping by combining 1/3 cup packed light or dark brown sugar, 1 tablespoon granulated sugar, and 1 teaspoon ground cinnamon in a bowl. Add 1/4 cup melted unsalted butter and stir in 2/3 cup all-purpose flour with a fork until it becomes crumbly, then set it aside for later.

3-In a separate bowl, whisk together the dry ingredients: 1 and 3/4 cups all-purpose flour, 1 teaspoon baking soda, 1 teaspoon baking powder, 1 teaspoon ground cinnamon, and 1/2 teaspoon salt. This ensures everything mixes evenly and helps the muffins rise properly. Using a mixer, beat 1/2 cup softened unsalted butter with 1/2 cup packed light or dark brown sugar and 1/4 cup granulated sugar until creamy, which takes about 3 minutes.

4-Add 2 large eggs at room temperature, 1/2 cup yogurt or sour cream, and 2 teaspoons pure vanilla extract to the butter mixture, beating until fully combined. Then, on low speed, incorporate the dry ingredients along with 1/4 cup milk until just mixed, and gently fold in 1 and 1/2 cups of chopped apples. This step keeps the batter thick and prevents overmixing, which can make the muffins tough.

5-Fill your muffin cups to the top with the batter and spoon the crumb topping evenly over each one, pressing it gently to stick. Bake at 425°F (220°C) for the first 5 minutes to get that perfect rise, then reduce the heat to 350°F (175°C) and continue baking for 15-18 minutes, or until a toothpick comes out clean. Let the muffins cool in the pan for 5 minutes before transferring to a wire rack, and if desired, whisk together the optional icing with 1 cup confectioners’ sugar, 3 tablespoons heavy cream or milk, and 1/2 teaspoon pure vanilla extract to drizzle on top.