The Best Oatmeal M&M Chocolate Chip Cookies

INGREDIENTS

large egg

1/2 cup

unsalted butter (1 stick)

1/2 cup

light brown sugar, packed

1/4 cup

granulated sugar

1 tbsp

vanilla extract

1 1/2 cups

old-fashioned whole rolled oats (not instant or quick cook)

3/4 cup

all-purpose flour

1/2 tsp

baking soda

1/2 tsp

salt, or to taste

1 cup

M&Ms (I used plain), plus more for the tops

1/2

cup semi-sweet chocolate chips