Melt the butter in the bottom of a large pot or dutch oven over medium-high heat. Add the onions and saute for about 5 minutes until softened and translucent. Add the garlic and saute another 30 seconds.
2 Tablespoons salted butter, 1 medium onion, 2 cloves garlic
Sprinkle the flour over the onions and cook for 1 minute, whisking to coat the flour. Whisk in the half-and-half, then the chicken broth. Season with the salt and pepper.
1/4 cup all-purpose flour, 2 cups half-and-half or whole milk, 3 cups chicken broth, 1 teaspoon kosher salt, Pinch of black pepper
Add the cauliflower and bring to a boil. Once boiling, reduce the heat to medium-low and cook, stirring occasionally, for about 15 minutes until the cauliflower is soft and cooked through.
2 pounds cauliflower
Blend the soup using either an immersion blender or by transferring part of the soup to a blender with the lid tilted to an angle to allow steam to escape. Work in batches until all of the soup is smooth, then return it to the pot.
Heat the soup over medium heat and stir in the dijon mustard and cheeses until melted.
1 teaspoon dijon mustard, 1 cup shredded white cheddar cheese, 1 cup shredded pepper jack cheese
Serve with additional shredded cheese sprinkled on top. Additional toppings like chopped green onions and crumbled bacon are also really good.
Chopped green onions, Crispy crumbled bacon, Additional cheese