½ cup/1 stick unsalted butter, softened
½ cup granulated sugar
¼ packed cup light brown sugar
2 large eggs, at room temperature
½ cup plus 2 tablespoons sour cream, at room temperature
2 tablespoons whole milk
1 teaspoon vanilla extract
1 ⅔ cups all-purpose flour
scant ⅓ cup almond flour
1 teaspoon baking powder
1 teaspoon baking sode
1 pinch table salt
¾ cup blueberries, fresh or frozen
2 tablespoons plus 1 teaspoon blueberry or raspberry jam
Almond Topping
¼ packed cup light brown sugar
2 tablespoons all-purpose flour
2 tablespoons almond flour
1 ½ tablespoons unsalted butter, cold and cut into small cubes
3 tablespoons sliced almonds
Heat the oven to 355°F. Line two 12-cup muffin tin with 14 paper liners (the bottoms of the baked muffins are quite moist, so paper liners are preferable to butter or baking spray).
Make the topping. In a medium bowl mix together the 50 grams (¼ packed cup) brown sugar, 15 grams (2 tablespoons) all-purpose flour, and 12 grams (2 tablespoons) almond flour. Use your fingers to rub in the cold butter until the mixture forms coarse crumbs. Add the sliced almonds and toss to combine, then place the crumb topping in the refrigerator while you prepare the muffin batter.
Make the muffin batter
. In a large bowl, with a whisk or an electric hand mixer on low, beat the softened butter, granulated sugar, and 50 grams (¼ packed cup) brown sugar until light and creamy, about 2 minutes. Beat in the eggs one at a time, scraping down the bowl after each addition. Add the sour cream, milk, and vanilla and beat until smooth and combined.
In a medium bowl, whisk together the 200 grams (1 ⅔ cups) all-purpose flour, the 32 grams (scant ⅓ cup) almond flour, baking powder, baking soda, and salt. Add the flour mixture to the large bowl and beat just until combined and no flour streaks remain. Gently fold in the blueberries with a rubber spatula.
Divide the batter evenly between the muffin tins. Spoon ½ teaspoon of jam on top of each muffin and use an offset spatula or a butter knife to smooth the batter. Sprinkle the chilled topping over each muffin. Bake for 20 to 22 minutes, until the muffins are golden, set, and spring back when lightly poked. Let the muffins cool in the tin for 10 minutes before removing and letting them cool completely on a wire rack.