Soft and Chewy Snickers Chocolate Chip Cookies

unsalted butter, softened

light brown sugar, packed

granulated sugar

large egg

vanilla extract

all-purpose flour

cornstarch

baking soda

salt, optional and to taste

heaping cup Snickers, diced small and loosely piled in measuring cup (or another variety of candy including M&Ms, Milky Way, Peanut Butter Cups, Rolo, etc.)

semi-sweet chocolate chips