1. Pour oil into a 12-inch frying pan with 2-inch-high sides over medium heat. When hot, add garlic and stir until fragrant but not brown, about 1 minute. Add cauliflower and stir to coat, about 1 minute.
2. Stir in pasta and 3 1/2 cups water. Bring to a simmer over high heat, then cover, reduce heat, and cook, stirring often, until pasta is just tender to bite and liquid has reduced to a creamy sauce, 15 to 20 minutes; if mixture begins to stick before pasta is done, add more water 1/2 cup at a time. Stir in cheese and add salt and pepper to taste.