Step 1

In a large saucepan, heat butter and oil over medium-high heat. Add cauliflower and onion; cook and stir until crisp-tender, 8-10 minutes. Add garlic; cook 1 minute longer. Stir in flour until blended; gradually whisk in broth. Bring to a boil, stirring constantly; cook and stir until cauliflower is tender, 12-15 minutes.

Step 2

Puree soup using an immersion blender. Or, cool soup slightly and puree in batches in a blender; return to pan. Stir in chicken, cream, ham, mustard, salt and pepper; heat through. Stir in cheese until melted.