1. Preheat oven to 350°F (180°C). Placed mashed potatoes on the bottom of an oven-to-tableware dish or a 9- x 13-inch (20- x 30-cm) baking pan, or divide among 12 ramekins.
2. Smooth so that it’s even on top (an easy way to do this is with a layer of parchment paper). Sprinkle with half the shredded cheese.
3. Add the broccoli mixture and top with remaining cheese. Bake, uncovered, for 30 minutes.