Heat oven to 350°F. Make brownies as directed on box for 9-inch pan, except stir 1/2 cup chocolate chips into batter before spreading in pan. Cool 15 minutes on cooling rack.
Spread hot fudge over brownies. Place in freezer 30 minutes. Spread yogurt evenly on top. Sprinkle with 2 tablespoons chocolate chips. Place in freezer about 4 hours or until firm.
Just before serving, cut into 9 pieces. Store any remaining dessert tightly covered in freezer up to 1 week.