Cream together butter and both sugars; add egg and vanilla.

In a small bowl, whisk together salt, baking soda, and pudding. Add the dry mixture to the butter mixture, then slowly add flour.

Add M&M's to the dough with a wooden spoon. Cover and place in the refrigerator while the oven heats to 375°.

Drop dough by the spoonful or with a cookie scoop onto a greased cookie sheet. Bake 7-8 minutes, or until lightly golden on top.