Cauliflower & Cheese Bake

Name: Cauliflower & Cheese Bake
Ingredients: 1 bag steamed cauliflower (or head of fresh cauliflower, chopped and steamed); 1 small onion, chopped; 1/3 cup grated parmesan cheese; 2 tsp dry mustard; 2 tbsp unsweetend, unflavored almond milk; 1/3 cup reduced fat cheddar cheese