Preheat the oven to 375°F. Line two baking sheets with silicone baking mats or parchment paper and set aside. In a large bowl, cream together the butter and sugars with beaters. Mix for 1-2 minutes, or until creamy and fluffy. Add the eggs and vanilla and mix just until combined.
Add the flour, baking soda and salt and mix just until combined. Fold in the chocolate chips and M&M’s. Refrigerate dough for 15 to 30 minutes if time allows.
Using a large cookie scoop (about 3 Tablespoons), scoop the cookie dough onto the baking sheet about 2 inches apart. Place any extra chocolate chips or M&M’s on the top of the cookies if desired.
Bake for 7-10 minutes, or until the edges are barely golden brown. Allow cookies to set on pan for 2-3 minutes, and then remove to a cooling rack.
Storage:Store once cooled in an airtight container for up to 3 days. Freeze for up to 3 months. Remove from freezer and hour before ready to serve or microwave for 10 to 15 seconds.