Rice Krispy Treats

3 Tbs Butter or Margarine
5 ½ -6 cups mini marshmallows a (or 40 large marshmallows, or 11 Jumbo ones)
6 cups rice krispy cereal

Melt butter in large, nonstick pan over low heat. Add marshmallows and stir until almost completely melted. Remove from heat, and continue stirring until completely melted. Add cereal immediately, mix well, and pressed into greased or buttered 9x13 pan. Let cool and cut into squares.