• Preheat the oven to 375°F. Line a 12-cup muffin pan with paper liners or grease the cups.
• Prepare the streusel by combining the brown sugar, flour, and cinnamon in a small bowl. Cut in the cold butter with a fork or pastry cutter until coarse crumbs form. Refrigerate while preparing the muffin batter.50 g light brown sugar,35 g freshly milled soft white wheat flour,2 g ground cinnamon,2 Tbsp cold salted butter.
• In a large bowl, whisk together both freshly milled flours, brown sugar, granulated sugar, baking powder, baking soda, cinnamon, and salt.220 g freshly milled soft white wheat flour,30 g freshly milled hard white wheat flour,60 g light brown sugar,110 g granulated sugar,7 g baking powder,3 g baking soda,3 g ground cinnamon,3 g salt.
• In a separate bowl, whisk together the eggs, buttermilk, melted butter, and vanilla extract.2 large eggs,110 g full-fat buttermilk,6 Tbsp salted butter,5 g vanilla extract.
• Pour the wet ingredients into the dry ingredients and gently stir until just combined. Fold in the diced apples. Do not over mix.190 g Granny Smith apples.
• Divide the batter evenly among the 12 muffin cups, filling each about 3/4 full. Sprinkle the chilled streusel evenly over the tops without pressing it into the batter.
• Bake for 17–20 minutes, or until the tops spring back lightly when touched and a toothpick inserted into the center comes out clean or with a few moist crumbs.
• Let the muffins cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

Optional Vanilla Glaze

• Whisk together the powdered sugar and milk until smooth, adding just enough milk to make a thick but pourable glaze.60 g powdered sugar,2-3 tsp milk.
• Drizzle lightly over the cooled muffins.