Freeze the almonds for 30 minutes, preheat the oven to 325 degrees and line 2 baking sheets with baking parchment

In a food processor, combine the almonds and the confectioners sugar and pulse on and off for 40 seconds, or until powdery. Add the cocoa powder and pulse very briefly just to mix.

In a large mixing bowl, beat the egg whites to very soft peaks and beat in the granulated sugar until the mixture is glossy, 1 minute, more. Sieve the almond-cocoa mixture over the egg whites and gently fold it in, being careful not to crush too much air out of the egg whites. Using a piping bag fitted with a 1/2-inch plain tip, pipe 1 1/2-inch circles of the mixture onto the parchment-lined baking sheets. Very gently poke a whole almond into the top of each one. Bake in the oven for 25 to 30 minutes, or until firm, turning the pans around halfway through the cooking time to cook them evenly. Transfer the sheets of paper onto damp tea towels and let stand for 5 minutes, then peel the macaroons off and finish cooling them on a rack. Serve at room temperature or store in an airtight tin, layered with sheets of waxed paper, for up to 2 weeks.