Makes 12 standard-size muffins
For the topping
1/4 cup (1 1/2 ounces) all purpose flour
2 tablespoons granulated sugar
2 tablespoons firmly packed light brown sugar
1/4 teaspoon ground cinnamon
2 tablespoons cold unsalted butter, cut into small pieces
For the muffins
7 tablespoons (3 1/2 ounces) unsalted butter, room temperature
3/4 cup (6 ounces) granulated sugar
2 large eggs
2 1/4 cups (11 1/2 ounces) all purpose flour
4 teaspoons baking powder
1/2 teaspoon salt
1 cup (8 fl. ounces) milk
1 1/2 teaspoons vanilla
1 1/2 cups (6 ounces blueberries or a combination of blueberries and blackberries, fresh or frozen, unsweetened and unthawed)
Preheat the oven to 375 degrees. Grease with butter or nonstick cooking spray 12 standard size muffin cups.
To make the topping, stir together the flour, granulated sugar, brown sugar and cinnamon in a small bowl. Using your fingers or a pastry cutter, rub or cut the butter into the dry ingredients until coarse crumbs form. Alternatively, combine all ingredients in a food processor and pulse just until coarse crumbs form.
For the muffins, in a bowl, using an electric mixer on medium speed, or using a stand mixer with the paddle attachment, cream together the butter and sugar until light and fluffy. Add the eggs, one at a time, beating well after each addition until blended into the butter mixture.
In a separate bowl, stir together the flour, baking powder and salt. In two increments, add the dry ingredients and the milk and vanilla to the butter mixture, alternating between the dry ingredients and the milk and vanilla. Stir just until even moistened. The batter will be fairly thick. Gently fold in the berries just until evenly distributed, taking care not to break up the fruit. It should take just a few folds, avoid overmixing.
Spoon the batter into each muffin cup, filling it to level with the rim of the cup. Sprinkle each muffin with some topping.
Bake the muffins until golden, dry and springy to the touch, about 20-25 minutes. A toothpick inserted into the center of a muffin should come out clean. Transfer the pan to a wire rack, let cool for 5 minutes. Unmold the muffins, serve warm or at room temperature.
Note: Muffins may be frozen. Reheat in foil at 300 degrees for about 15 minutes. Remove from foil and continue heating, uncovered, for another five minutes.
Recipe adapted from Williams-Sonoma Muffins.