In a large mixing bowl, beat butter and sugar until light and fluffy.
Add eggs and vanilla and beat well.
In another bowl, stir together flour, cocoa, baking soda and salt. Gradually add this to the butter mixture.
The mixture will be THICK.
Heat oven to 350 degrees F.
Chill in refrigerator 10 minutes.
I used a regular sized ice cream scoop for extra large cookies.
Drop dough onto a greased, cold cookie sheet.
Bake 17 minutes at 350 degrees for crisp edges and gooey centers.
Remove from oven and allow cookies to sit on cookie sheet 2 minutes before removing.
After 2 minutes, using a thin spatula, move to a wire rack to cool.
Microwave frosting 30 seconds just to make it easier to blend. Stir.
Stir in crisp rice cereal.
Stir together first 3 ingredients in a sauce pan over medium heat until butter is melted. Cook, stirring constantly, 2 minutes or until slightly thick. Remove from heat. Whisk in powdered sugar and vanilla. Whisk until smooth.