Preheat oven to 350 degrees. Grease muffin pan and set aside.
Stir together almonds, powdered sugar, cocoa, orange zest, 3 tablespoons butter, 1 egg white and tablespoon water in a medium bowl. In another bowl, whisk remaining egg white and granulated sugar until medium peaks form; fold into cocoa mixture. Spoon mixture into prepared muffin cups.
Bake until tops look dry, 10 to 12 minutes. Let cool 5 minutes, then turn out of pan.
Meanwhile, microwave remaining 1 tablespoon butter with chocolate in a small bowl until melted. Drizzle over warm brownies.