Meanwhile, in a large caste iron skillet or oven-safe saucepan over medium-low heat, sauté 2 Tbsp. garlic for the cauliflower “mashed potatoes” for 1-2 minutes of until soft. Put the softened garlic in a blender and set aside. Then, in the same skillet, add the onion, celery, carrot, mushrooms, and garlic and a small amount of olive oil and cook on medium heat until softened (7-10 minutes).