Heat oven to 400 degrees. 

Place cauliflower on a large rimmed baking sheet and drizzle with 2 tablespoons of olive oil. Sprinkle with salt and cayenne pepper and stir to coat.

Roast cauliflower for 20 minutes, stirring once halfway through cooking.

When cauliflower has finished roasted, add the remaining tablespoon of olive oil to a large soup pot or dutch oven over medium heat. 

Add the onion and garlic to the oil and cook for 5 minutes or until onions are soft and translucent.

Add the chicken broth to the pot along with the roasted cauliflower and bring to a boil. Reduce to a simmer and cook for 15 minutes.

Use a potato masher to the mash the cauliflower.

Stir in the heavy cream, cream cheese, and grated cheddar until smooth and creamy.

Serve with additional cheese, if desired.