Place cauliflower in a baking dish, drizzle oil and season with salt and pepper. Roast at 400 F for 15-20 minutes.
In a saucepan, heat oil on high. Add garlic and brown. Add half and half and bring to a boil. Make slurry by mixing cornstarch with 2 tbsp water. Then reduce to a simmer.
Add cheddar and stir 3-5 minutes until melted
When cauliflower is done, remove from oven and add slurry. Top with cheese and bake 15-20 minutes or until cheese browns.
Remove from oven, sprinkle black pepper over and let cool before serving.