Preheat the oven to 350°F.

Bring a pot of salted water to a boil. Add the cauliflower and cook until tender but firm, about 5 to 6 minutes. Drain.

To make the cheese sauce, place 2 tablespoons of butter in a small saucepan over medium-low heat. When the butter has melted, add the flour. Cook for 1 to 2 minutes, stirring or whisking constantly. Slowly add the milk as you continue to whisk. The sauce should thicken with each addition of milk. When all the milk has been incorporated, add 4 ounces of pepper jack cheese and stir until melted.

Place the boiled cauliflower in a large casserole dish. Pour the cheese sauce over the cauliflower. Sprinkle with the remaining 4 ounces of cheese.

Bake in the preheated oven for 15 minutes, until the cheese is lightly browned.