Bring a large pot of water to a boil. Wash a large head of cauliflower and cut it into bite-sized florets, and place them into the boiling water for 5 minutes before draining well. Transfer the drained blanched cauliflower to a bowl.
Make the cheese sauce
To make the vegan cheese sauce, to a pan add a can of coconut milk, 1/2 cup of water, 1/3 cup nutritional yeast, 1 tablespoon tapioca starch, 1 tablespoon corn starch, 1 1/4 teaspoon salt, 1 teaspoon lemon juice, 1/2 teaspoon paprika, 1/4 teaspoon onion powder, 1/4 teaspoon garlic powder, 1/8 teaspoon of turmeric and give it a stir with a whisk until all of the starch is dissolved.
Turn the stove to medium heat and frequently stir until your cheese sauce thickens and starts to boil. Then turn down the heat and stir constantly for 1 minute before taking off the heat.
Pour the hot cheese sauce over the cauliflower florets and mix well. Then transfer the mixture to a greased casserole dish.
For the breadcrumb topping
Melt 3 tablespoons of vegan butter, then add 1/2 teaspoon of garlic powder and 1 cup of bread crumbs or crushed crackers to the melted butter. Then sprinkle the breadcrumb mixture onto the top of the casserole.
Bake in the oven at 375° F (190° C) for 30 minutes until bubbly and golden brown.
Notes
Use full-fat coconut milk for the creamiest cheese sauce.
Add the tapioca and corn starch to cold coconut milk. If you try to add this after you start heating the sauce, it will clump and not dissolve.
You can omit the process of blanching the cauliflower before baking, but you will have to bake it for an extra 20 minutes if you skip this step.
For an extra cheesy sauce, add 1 cup of vegan shredded cheddar cheese to the sauce and stir until it melts completely.