Step 1

Preheat the oven to 400 degrees F.

Step 2

Arrange the chopped cauliflower and garlic cloves on a large baking sheet. Drizzle with the olive oil, season with a pinch of salt and pepper, and toss to coat. Spread into a single layer. Roast for 20 to 25 minutes, stirring once halfway through. Set aside to cool. When cool enough to handle, remove the garlic from its skin and finely chop.

Step 3

In a large pot, melt the butter over medium-high heat. Add the onion and cook for 2 to 3 minutes, until just beginning to soften. Add the carrots and celery, and cook for 5 minutes, stirring occasionally. Stir in the chopped garlic, cauliflower, bay leaf, and thyme. Sprinkle the flour over the vegetables and mix to combine.

Step 4

Cook until the flour disappears, about 2 minutes. Pour in the broth, stir, and bring to a simmer. Cook for 10 minutes. Stir in the milk and cheese, and continue mixing until the cheese is melted and the chowder is creamy, 2 to 3 minutes. Discard the bay leaf. If you'd like your soup thicker or creamier, use an immersion blender to puree it until it reaches your desired consistency (Alternatively, you can ladle a few scoops into a blender and puree a few batches. Be careful not to fill your blender more than halfway, as hot liquids like to splatter). Season with salt and pepper to taste. Ladle the chowder into bowls, and serve warm.