To make the sauce, heat one tablespoon of oil in a large skillet over medium heat. Add the garlic and onions and sauté for 2-3 minutes, until the onions become translucent and fragrant. Remove from heat and add the onions and garlic, along with the non-dairy milk, vegetable broth, hemp hearts, nutritional yeast, vegan parmesan (if using), salt, and pepper, to a blender. Blend for 1-2 minutes until the sauce is smooth and creamy. Taste and adjust seasonings.