Step 5
Mashed Potatoes with Roasted Cauliflower: Put oven rack in top third of oven and preheat to 450℉. Place 12 cups cauliflower florets, cut no larger than 1 in., on a rimmed baking sheet. Toss with 2 tbsp. extra-virgin olive oil and 1/2 tsp. each kosher salt and pepper to coat evenly. Spread in a single layer and roast until cauliflower is very tender and brown on the edges, turning occasionally, about 25 minutes. Set aside about 1/3 cup of the best-looking florets, then coarsely mash remaining florets on baking sheet with a potato masher. In step 2, mix mashed florets and 1/2 cup warmed milk (not 1 cup as in the basic recipe) into mashed potatoes. Add 2 tbsp. unsalted butter, 1 1/2 tsp. salt, and pepper to taste. Top with reserved cauliflower and 1 tbsp. butter. Make ahead: Cauliflower, up to 3 days, chilled; reheat before using.