I have no idea if this one is already posted since I couldn't search for M&Ms. Another recipe I collected at Christmas time and can't remember where it comes from.
- Preheat oven to 350°F.
- Cream butter and sugar together; add egg and vanilla and beat until light and fluffy.
- In a separate bowl, combine flour, cooca, baking soda, and salt; gradually blend into creamed mixture.
- Stir in M&Ms until evenly distributed.
- Drop by spoonfuls about 2-inches apart onto an ungreased cookie sheet.
- Bake 9-13 muinutes.
- Cool and store in an airtight container.