Preheat oven to 350 degrees F.

Grease cookie sheets using preferred method.

In a medium sized mixing bowl, sift together 2 1/2 cups flour, baking soda and salt.

In a large mixing bowl, using a mixer on medium speed, beat together butter, peanut butter, sugar and granulated sugar until creamy, about 2 minutes.

Beat in eggs and vanilla until well combined.

Reduce mixer speed to low and gradually beat in flour mixture until combined.

Divide dough into two bowls.

In one bowl, beat in additional 1/4 cup flour until combined; stir in 1/2 cup M&M's.

In additional bowl, beat in cocoa powder until combined; stir in 1/2 cup M&M's.

Lightly cover dough and chill in the refrigerator or freezer until firm, about 15 minutes.

Form dough into two balls, shape into logs, and wrap in separate pieces of plastic wrap; chill for 10 minutes.

Place additional 1/2 cup peanut M&M's in a plastic bag and crush with a rolling pin.

Remove cookie dough logs from freezer, press together, and roll into crushed M&M's to coat the outside.

Cut log in half, wrap logs in plastic wrap, and chill for 10 additional minutes.

Slice logs into 1/2-inch thick rounds, place on cookie sheets, and bake for 14-15 minutes, or until golden brown around edges.

Cool 1 minute before transferring to wire racks to cool completely.