In a bowl, beat the egg white to very stiff peaks. Continue beating, while adding the sugar 1 spoonful at a time, until very thick and glossy. In another bowl, stir the almonds with the sugar, cinnamon and bitter almond oil. Gently fold the almond mixture into the egg whites until thoroughly combined.
Place the mixture in a piping bag fitted with a round 7 mm (approximately 1/4 inch) tip. Pipe walnut-sized portions onto a parchment-lined baking sheet.
Bake in a 160°C (approximately 325°F) oven for 15 minutes. The cookies should not color too much.
Remove the cookies from the oven and allow to cool on a wire rack. Serve dusted with powdered sugar.