Sauté Aromatics: Melt butter in a large heavy-bottomed Dutch oven or stockpot over medium heat. Add diced onion and sauté for 4 to 5 minutes until soft and translucent. Add minced garlic and cook for 1 minute until fragrant.

Whisk the Golden Roux: Sprinkle all-purpose flour over the sautéed onions and stir continuously for 1 to 2 minutes to cook out the raw flour flavor and create a light golden paste.

Simmer Broth & Veggies: Slowly pour in the halal chicken bone broth and heavy cream while whisking constantly to create a silky, lump-free base. Whisk in mustard powder, nutmeg, salt, and black pepper. Bring to a gentle boil, then reduce heat to medium-low. Add chopped broccoli florets and matchstick carrots. Simmer uncovered for 15 to 18 minutes until broccoli is fork-tender and the soup has thickened.

Melt Cheese on Low Heat (Anti-Curdle Rule): Turn the heat to the lowest setting (or remove pot from heat). Gradually fold in the freshly grated sharp cheddar and white cheddar by the handful, stirring gently in one direction until completely melted into a velvety smooth sauce. Do not boil after adding cheese!

Serve in Warm Bread Bowls: Ladle steaming soup into hollowed-out sourdough bread bowls or wide ceramic bowls. Garnish with a pinch of extra cheddar and cracked black pepper. Serve hot immediately!