Tender whole-wheat muffins studded with juicy blueberries and crowned with a buttery cinnamon streusel, offering a wholesome nuttiness and a delicate crunch in each bite.
Preheat oven to 375°F (190°C). Line a 12-cup muffin pan with paper liners or grease well.
Make the streusel: In a small bowl, combine 1/4 cup flour, brown sugar, granulated sugar, cinnamon, and a pinch of salt. Cut in the cold butter until dime-sized crumbs form; set aside.
In a large bowl, whisk together the flour, sugar, baking powder, and salt.
In a separate bowl, whisk the eggs, melted butter, vanilla, and milk until well combined.
Pour the wet ingredients into the dry and stir gently just until no dry streaks remain; do not overmix.
Fold in the blueberries gently to avoid bursting.
Divide batter among prepared muffin cups, filling about 2/3 full.
Sprinkle streusel evenly over the tops of the muffins.
Bake 22–25 minutes, until golden and a toothpick inserted in the center comes out clean.
Cool in the pan briefly, then transfer to a wire rack to cool slightly. Serve warm or at room temperature.