How to Make It
Preheat the oven to 350°. Spread the almonds in a pie plate and bake for about 5 minutes, or until toasted. Let cool, then coarsely crumble the nuts with your fingers.
Butter 2 large heavy cookie sheets. In a medium bowl, whisk the egg whites with the sugar and almonds just until combined. Stir in the butter and vanilla, then stir in the flour.
Drop rounded tablespoons of the batter onto the cookie sheets, about 3 1/2 inches apart. Using the back of the spoon, spread the batter evenly into 3-inch rounds. Bake for about 13 minutes, or until golden. Using a metal spatula, quickly transfer the cookies to a rack or drape them over rolling pins or glasses until cool. Repeat with the remaining cookie batter.