Beat egg whites until soft peaks form; beat in sugar 2 Tbsp at a time, until stiff, glossy peaks form. Beat in almond extract. Fold in ground almonds.
Drop by generous generous tablespoon-fulls (or use piping bag) onto parchment lined baking sheets. Sprinkle sugar over cookies.
Bake at 300F (150C) in top & bottom third of oven, rotating & switching pans half-way through, for about 20mins or until firm to touch & light golden.Transfer to rack & let cool completely before serving.