01 -
Preheat the oven to 180 degrees Celsius (350 degrees Fahrenheit).
02 -
Slice the top off the garlic bulbs, about 2 to 3 centimeters from the top to expose the cloves.
03 -
Place garlic bulbs, cauliflower, and thyme in a large baking dish. Drizzle with 2 tablespoons olive oil and season generously with salt and pepper. Bake for 45 minutes.
04 -
Set aside 4 small cauliflower florets for garnish. Allow garlic to cool slightly and squeeze out the roasted cloves from the skins.
05 -
Heat remaining 2 tablespoons of olive oil in a large pot over medium heat. Add leeks and cook for about 5 minutes until slightly wilted, stirring occasionally.
06 -
Add roasted cauliflower, garlic cloves, and baking dish juices to the pot along with the stock and additional salt and pepper. Bring to a boil, then reduce heat and simmer uncovered for 20 minutes.
07 -
Remove from heat and let cool slightly. Use an immersion blender or blender to puree until smooth and silky.
08 -
Stir in cream if using. Garnish with a drizzle of olive oil, reserved cauliflower florets, and thyme leaves.
09 -
Spread butter on both sides of each bread slice. Layer cheddar, mozzarella, and parmesan evenly between two sandwiches.
10 -
Heat a skillet over low-medium heat and lightly drizzle with olive oil. Cook sandwiches for 5 minutes per side until golden and cheese is melted.
11 -
Cut grilled cheeses in half and serve hot with the cauliflower soup.