Blanch and toast the almonds. Peel and chop them very finely or crush them in a mortar with 1/2 cup sugar. Add the vanilla, beat egg whites till stiffened, then fold in the almonds. Spoon the batter into a pastry bag fitted with a plain tip. Pipe 2 l/2-in. wide rounds about 1 1/2 apart on a buttered baking sheet and flatten them a bit. Sift the confectioner's sugar over the tops and let stand at room temperature 1-2 hours. Pre-heat the oven to 350ºF and bake for about 20 mins. Remove from oven and cool.