Preheat oven to 165 degrees C (325 degrees F). Line 2 cookie trays with foil; lightly grease foil.
Mix almond paste and caster sugar in food processor until smooth. Add icing sugar and 2 egg whites; process until smooth.
Whisk remaining 2 egg whites in small bowl. Place pine nuts on shallow plate. With lightly floured hands roll dough into 2.5cm balls. Coat balls in egg whites, shaking off excess, then roll in pine nuts, pressing lightly to stick. Arrange balls on cookie trays, and flatten slightly to form a 4cm round.
Bake 15 to 18 minutes in the preheated oven, or until lightly browned. Let stand on cookie sheet 1 minute. Transfer to wire rack to cool.