Take them out of the oven when they are dry around edges but still somewhat wet-looking in the middle. They will fall apart if you try to eat them warm (gooey but yummy!), but are nice and soft if saving some for next day.
Shape dough into 1 1/2-inch balls. Place on cookie sheet 3 inches apart. Press each ball slightly to flatten then press the M&Ms™ candies into top of the cookies. Cover cookie sheets with plastic wrap and refrigerate 2 hours.
Can be made in advance and stored, layered between wax paper in an airtight container, up to 3 days at room temperature. Alternatively you can freeze your baked cookies up to 3 months.