White Chocolate Raspberry Cupcakes

For cupcakes: Preheat oven to 325°. Line twenty-four 2-1/2-inch muffin cups with paper bake cups; set aside. Sift flour, baking powder and 1 teaspoon kosher salt into a medium bowl. Whisk in chocolate.

In a large bowl, beat 2 cups sugar, the sour cream, oil, whole eggs and 1 tablespoon vanilla with an electric mixer on medium speed for 2 minutes.

In another large bowl, beat six egg whites with clean beaters until very foamy, about 1 minute. Add to sour cream mixture and beat until combined. Add flour mixture and beat on low speed just until combined. Divide batter evenly among cups. Sprinkle a few partially thawed raspberries on each.

Bake 15 minutes. Rotate pans and bake 5 to 7 minutes longer or until a toothpick inserted in centers comes out clean. Cool in cups on wire racks for 5 minutes. Remove from cups; cool completely.

For sauce: In a small saucepan, bring the 1-1/2 cups frozen raspberries and 3 tablespoons sugar to a simmer over medium heat. Cook for 5 minutes; cool slightly. Transfer to a blender or food processor and puree for 1 minute. Strain through a fine-mesh sieve. Transfer to a resealable plastic bag; store in refrigerator.

For Swiss meringue buttercream: Set the metal bowl of a stand mixer over a saucepan containing an inch or so of water to create a double-boiler. In the bowl, combine remaining six egg whites, 2-1/4 cups sugar and a dash of salt. Cook, whisking constantly, until an instant-read thermometer registers 160°, about 10 minutes. Attach bowl to mixer fitted with whisk. Beat until meringue is thick and glossy and the bottom of the bowl feels cool to the touch. (This can take up to 15 minutes.) Switch to paddle attachment. With mixer on low, add butter, 1 tablespoon at a time, until incorporated. The mixture may look curdled, but keep beating until smooth. If the mixture is too runny, refrigerate for about 15 minutes, then continue beating. Beat in the remaining 1 tablespoon vanilla.

Transfer frosting to a pastry bag fitted with a star tip and pipe swirls on cupcakes. Snip a tiny corner from the plastic bag and drizzle raspberry sauce over cupcakes. Garnish with white chocolate curls. Serve immediately.