Heat oven to 400 degrees F (204 C). Slice off the very top of the head of garlic and set on a piece of foil. Drizzle the top with oil and wrap to conceal. Then roast directly on a center oven rack for ~50 minutes to 1 hour, or until the cloves are tender, fragrant, and light golden brown.
Soak cashews in very hot water (uncovered) for at least 30 minutes.
Drain your soaked cashews and add to a small blender along with roasted garlic (cool slightly then squeeze up from the bottom toward the top to remove cloves), olive oil, nutritional yeast, salt, and water. Blend on high until creamy and smooth.
Taste and adjust seasonings as needed, adding more salt to taste or nutritional yeast for cheesiness. The roasted garlic should add a nice caramelized, garlicky sweetness to the sauce, but if you prefer a more garlicky punch, you could throw in 1-2 raw garlic cloves and blend. Set aside.
Best when fresh. Ideal for adding to dishes like moussaka, as a mac ‘n’ cheese base, in vegetable bakes, and more. Leftovers will keep in the refrigerator for up to 3-4 days, or in the freezer for up to 1 month. When reheating, add more water or plain dairy-free milk as needed to thin.
*Prep time includes soaking cashews. *Nutrition information is a rough estimate.