Preheat the oven to 450 degrees F (232 degrees C).
Line a baking sheet with foil or parchment paper.Melt 2 tablespoons (28 g) of butter.
In a large bowl, toss together the cauliflower florets with the melted butter.
Season with sea salt and black pepper.Arrange the cauliflower florets on the prepared baking sheet.
Roast for about 10-15 minutes, until crisp-tender.Heat the cheddar cheese, heavy cream, milk, and remaining tablespoon of butter, stirring frequently.
(You can do this on the stove in a double broiler, or in the microwave.) Heat until the cheese mixture is smooth.