Bring a large pot of boiling water to a boil. Add the cauliflower and cook, covered, for 8-10 minutes or until cauliflower is fork tender. Reserve 1 cup of the boiling water.
Heat the olive oil a large skillet over medium heat, sauté the minced garlic until soft and fragrant, but not browned, about 1-2 minutes.
Use a slotted spoon to transfer the cooked cauliflower to a blender. Add the sautéed garlic, reserved 1 cup cooking liquid, milk, salt and pepper. Cover the vent in your blender lid with a thin kitchen towel to allow venting and puree until the sauce is smooth and creamy, about 1 minute. If the sauce starts to look dry, add a few drops of water, milk, or olive oil.
Serve with cooked fettuccine