from David Lebovitz
1 cup (100 gr) powdered sugar
½ cup powdered almonds (about 2 ounces , 50 gr, sliced almonds, pulverized)
3 tablespoons (25 gr) unsweetened Dutch-process cocoa powder
2 large egg whites, at room temperature
5 tablespoons (65 gr) granulated sugar
½ cup (125 ml) heavy cream
2 teaspoons light corn syrup
4 ounces (120 gr) bittersweet or semisweet chocolate, finely chopped
1 tablespoon (15 gr) butter, cut into small pieces
Preheat oven to 375 degrees F (180 degrees C).
Line two baking sheets with parchment paper and have a pastry bag with a plain tip (about 1/2-inch, 2 cm) ready.
Using a food processor, grind together the powdered sugar with the almond powder and cocoa so there are no lumps. Beat the egg whites until they begin to rise and hold their shape. While whipping, beat in the granulated sugar until very stiff and firm, about 2 minutes.
Carefully fold the dry ingredients, in two batches, into the beaten egg whites with a flexible rubber spatula. When the mixture is just smooth and there are no streaks of egg white, stop folding and scrape the batter into the pastry bag.
Pipe the batter on the parchment-lined baking sheets in 1-inch (3 cm) circles (about 1 tablespoon each of batter), evenly spaced one-inch (3 cm) apart.
Rap the baking sheet a few times firmly on the countertop to flatten the macarons, then bake them for 15-18 minutes. Let cool completely then remove from baking sheet.
Fill with chocolate or jam and let sit overnight to let the flavors meld.