- Preheat oven to 375F and grease a 9x9 glass baking dish.
- Bring a large pot of water to a boil. Add cauliflower and 1/2 tsp salt and cook until cauliflower is just fork tender. Do not overcook.
- Drain cauliflower well and place back in the pot. Set aside.
- In a small saucepan, bring cream to a simmer, stirring well to avoid scorching.
- Whisk in cream cheese and mustard and stir until mixture thickens.
- Remove from heat and whisk in 1 cup shredded cheese and seasonings.
- Pour over cauliflower and gently mix to combine.
- Place cauliflower in prepared dish. Sprinkle with remaining cheese and bake until cheese is bubbly and slightly browned, or about 15 minutes.