1. Melt butter in a large saucepan on low heat.
2. Add large marshmallows. Cook until marshmallows are completely melted and mixture is well blended, stirring frequently. Remove from heat.
3. Add cereal; mix well.
4. Press mixture firmly into greased 13 x 9-inch pan.
5. Top with miniature marshmallows and press lightly onto cereal mixture.
6. Sprinkle cocoa mix evenly over top. Cool completely.
7. Cut into 24 squares to serve.
Easy Cleanup Tip: Line pan with foil before using to make cleanup a snap.