3/4 cup unsalted butter, softened (1 1/2 sticks)
3/4 cup light brown sugar, packed
1/4 cup granulated sugar
1 large egg
1 teaspoon vanilla extract
2 cups all-purpose flour
1/4 cup instant vanilla pudding mix (not sugar-free and not 'cook & serve'), OR use 2 teaspoons cornstarch in place of pudding mix
1 teaspoon baking soda
pinch salt, optional and to taste
3/4 cup semi-sweet chocolate chips
3/4 cup milk chocolate M&M's mixed into the dough + about 1/2 cup for placing on top of dough mounds