1/2 cup (2 oz./60 g) cake flour
5 Tbs. (1 oz./30 g) Dutch cocoa powder, plus more for dusting
1/2 tsp. baking powder
1/2 tsp. kosher salt
1 egg
1/4 cup plus 2 Tbs. (3 oz./90 g) granulated sugar
1 tsp. vanilla extract
5 Tbs. (2 1/2 oz./75 g) unsalted butter, melted and cooled slightly
Confectioners' sugar for dusting
Crushed freeze-fried raspberries for dusting (optional)
Position a rack in the lower third of an oven and preheat to 425°F (220°C). Place a Silpat nonstick heart mold on a baking sheet.
In a bowl, sift together the flour, cocoa powder and baking powder. Add the salt and whisk until combined.
In the bowl of a stand mixer fitted with the whisk attachment, beat together the egg and granulated sugar on medium speed until combined, about 30 seconds. Increase the mixer speed to high and beat until the mixture has quadrupled in volume, about 8 minutes. Reduce the mixer speed to low and beat in the vanilla.
Remove the bowl from the mixer and, using a rubber spatula, gently fold in the flour mixture until combined, then gently fold in the melted butter. Transfer the batter to a disposable pastry bag and cut the tip to form an opening about 1/2 inch (12 mm) wide. Using the pastry bag, fill each well of the mold about three-fourths full. Using your fingers, smooth the top of the batter in each well.
Bake until the madeleines spring back when lightly touched, 8 to 10 minutes. Remove the madeleines from the oven and immediately turn them out of the mold and onto a wire rack. Using a fine-mesh sieve, dust the madeleines with confectioners' sugar. If desired, use a fine-mesh sieve to dust the madeleines with the dried raspberries as well. Serve warm. Makes 24 mini madeleines.
– Williams Sonoma Test Kitchen