In a large bowl, cream butter, sugar, and brown sugar. Add egg and vanilla. Then add flour, pudding mix, baking soda and salt. Stir well until combined. Then add chocolate chip and M&M's.
Roll into 1 1/2 inch balls or use a medium cookie scoop. Bake 10-12 minutes until cooked through. Let cool on cookie sheet for about 10 minutes.
Notes
We typically use all-purpose flour for these cookies.Adapted From: Picky Palate