Soft M&M Chocolate Chip Cookies

unsalted butter, softened (1 1/2 sticks)

light brown sugar, packed

granulated sugar

large egg

vanilla extract

all-purpose flour

instant vanilla pudding mix (not sugar-free and not ‘cook & serve’), OR use 2 teaspoons cornstarch in place of pudding mix

baking soda

salt, optional and to taste

semi-sweet chocolate chips

milk chocolate M&M’s mixed into the dough + about 1/2 cup for placing on top of dough mounds