1. Stir together flour, ground almonds, baking powder, and salt; set aside.
2. In a mixing bowl cream butter and sugar at medium speed of electric hand held mixer. Beat in egg white and almond extract.
3. Stir flour and ground almond mixture into the creamed mixture. Cover with plastic wrap; chill for about 2 hours.
4. Shape dough into small balls, about 3/4-inch. Place balls 2 inches apart; flatten slightly with the bottom of a glass.
5. Press an almond into the centre of each cookie. Bake at 350°F, Gas Mark 4, 180 oC for about 12 minutes, or until set but not browned.
Makes about 4-dozen almond cookies.