Cut the top off of a bulb of garlic. Place it on a sheet of foil. Drizzle with olive oil, wrap and place in the oven to roast for 45 minutes or until garlic is soft and golden.
Place the cauliflower into a steamer and cook until soft.
Place chopped fennel into a skillet with a splash of oil. Add champagne. Season the monkfish with salt and pepper and place into the champagne bath. Poach for about ten minutes over medium heat. Do not let the champagne boil, but instead keep it just below a simmer
Dice prosciutto and add to a hot oiled pan. Add shallot to pan as fat is starting to separate from prosciutto. Add sherry vinegar, garlic, olive oil, and chili flakes. Finish with chopped chives. And place in a bowl.
Finish cauliflower purée. Place butter, steamed cauliflower, salt, and roasted garlic to a blender, blend until smooth, approximately one minute. If mix is too thick add some boiling water to get desired consistency.
Remove monkfish from poaching pan. Fish is cooked when it starts to open up, and has a little bounce when touched.
Slice poached fish into five centimeter chunks.
Plate on top of cauliflower purée, drizzle with vinaigrette and garnish with fennel frond.