Combine the sugar, 3 tablespoons of water and corn syrup in a small saucepan or caramel pot and stir to thoroughly moisten the sugar. Bring to a boil over medium heat. Wash down the walls of the pot with a moistened pastry brush to dissolve any sugar crystals that form there. Then continue boiling until the sugar reaches the firm-ball stage, or about 245 degrees F. Meanwhile, combine the almonds and confectioners' sugar in your food processor. When the syrup is ready, turn on the food processor and pour in the syrup. Continue process until the almonds paste is completely smooth. It will be hot. Transfer the almond paste to a stainless-steel bowl, cover it with a damp kitchen towel to prevent it from drying out, and let rest to room temperature. Place the almond paste on your countertop and gradually work in the liqueur by kneading it with the heel of your hand. Add sufficient liqueur to make the almond paste soft enough to pipe from a pastry bag, but not runny. Tint the almond paste green by kneading in 1 or 2 of green food coloring.
Recipe from The French Cookie Book, by Bruce Healy with Paul Bugat,