Set a large pot of water over high heat. Add the cauliflower florets and bring to a boil. Boil for 10 to 15 minutes until fork tender. Drain the cauliflower.
Put half of the florets in a food processor and pulse for 30 seconds. Add half of the melted butter, half of the cream and half of the sour cream and process until smooth. As you process, the mixture will work its way up the sides of the processor. When this happens, stop processing and push the mixture down using a rubber spatula.
Add half the salt and pepper to the cauliflower mixtures in the blender and pulse to combine. Pour the cauliflower mixture into a 13x9 inch baking dish.
Repeat with the remaining cauliflower, butter, cream, sour cream, salt and pepper, then add to the baking dish.
Smooth the top of mash with a rubber spatula, then top with shredded cheese and crumbled bacon. Broil for 2 to 4 minutes, until the cheese has melted and slightly browned. Sprinkle the top with chives and garnish each serving with a dollop of sour cream if desired.