Cooking spray
1/2 cup granulated sugar
1/2 cup packed dark brown sugar
3/4 cup water
1 tablespoon instant espresso or 2 tablespoons instant coffee granules
2/3 cup Dutch process or unsweetened cocoa
1/4 teaspoon salt
2 ounces semisweet chocolate, chopped
2 ounces unsweetened chocolate, chopped
2 tablespoons Kahlúa (coffee-flavored liqueur)
3 large egg yolks
1/3 cup sifted cake flour (such as Swan's Down)
6 large egg whites (at room temperature)
1/4 teaspoon cream of tartar
1/3 cup granulated sugar
1 tablespoon powdered sugar
1/4 cup raspberries (optional)
Chocolate curls (optional)