Beat margarine at medium speed of an electric mixer until creamy; gradually add sugar, beating well. Add egg substitute and flavoring; beat well. Combine flour and salt; gradually add to margarine mixture, beating well. Cover dough, and freeze 10 minutes.
Shape dough into 48 (1-inch) balls; roll in cereal. Place 2 inches apart on ungreased cookie sheets. Press thumb into each ball to make an indentation. Bake at 300° for 20 minutes. Remove from cookie sheets; let cool on wire racks. Fill each center with 1/2 teaspoon spread.