In a mixing bowl, beat cream cheese and margarine; blend in flour and salt. Chill for 1 hour. Shape into 1-inch balls; press into the bottom and up the sides of greased mini-muffin cups. For filling, beat the egg in a small mixing bowl. Add brown sugar, butter and vanilla; mix well. Stir in pecans. Spoon into shells. Bake at 325 for 25 – 30 minutes. Cool in pan on a wire rack. Decorate with maraschino cherries if desired.