2 heads cauliflower, rinsed and cut into florets (approximately 8 cups)
½ cup (50g) butter
½ cup (50g) flour
2 cups (475 ml) milk
1 teaspoon ground mustard
whole nutmeg (or substitute ½ teaspoon ground nutmeg)
1 cup grated sharp cheddar
1 cup grated sharp Gruyere, plus extra for topping
1 teaspoon salt
½ teaspoon ground black pepper
Preheat the oven to 350 degrees Fahrenheit (175 degrees Celsius). Grease a 9x13 baking dish with butter and set aside.
If you have a steamer, set it up to steam your cauliflower. If not, heat a medium pot filled halfway with water until it boil. Steam or boil the cauliflower. for 4-6 minutes, until it's cooked but still a little crisp. Drain the cauliflower using a colander and rinse with cold water to stop from cooking and set the colander over a bowl to let the cauliflower dry a little bit.
Melt the butter in a skillet over medium heat. Add the flour and mustard, stirring constantly to form a golden yellow paste that's a little bubbly around the edges. Slowly, slowly whisk in the milk, a little bit at a time, so that the milk and flour mixture form a silky sauce. Grate in a good portion of nutmeg and stir well. Keep stirring for a minute or two until the sauce is thickened and bubbly. Remove from heat.
Immediately stir in the grated cheeses until there's a smooth sauce. Remove the colander from the bowl it's resting on and dump out any water that's collected. Pour the cauliflower into the bowl and pour the cheese sauce over it. Fold the cauliflower and the cheese sauce together until the cauliflower is well coated, then transfer everything to the baking dish.
Sprinkle more grated Gruyere over the top and slide the baking dish into the oven to bake for 25-30 minutes until the top is golden brown. Remove from oven and serve immediately.
Recipe by Grits and Chopsticks at https://www.gritsandchopsticks.com/the-gravy-train/2019/01/cauliflower-cheese-cauliflower-gratin.html