Melt butter in saucepan over low heat. Add marshmallows and stir till melted. Cook 3 minutes, stirring constantly. Remove from heat, add Rice Krispies and stir till all are coated. Using buttered spatula, press evenly into buttered 13x9x2 inch pan. Cool. Cut into 2 inch squares.
VARIATIONS: - add 1 cup raisins - add 1 cup peanuts - add 1/4 cup peanut butter to marshmallows - melt 2 squares chocolate with marshmallows - for christmas add green food colouring (if desired), shape into trees or press into buttered ring or small bundt mold. Decorate with red cinnamon candies (for tree) or spearmint leaves and jelly berries for ring mold (resembles a wreath)