Place the cauliflower, cream and garlic in a large microwaveable dish. Cover and cook on high, stirring once, until tender, about 15 minutes.
Meanwhile, in a medium nonstick skillet, melt 5 tbsp. butter over medium-high heat. Cook, swirling the pan, until the butter turns golden, 3 to 4 minutes.
Using a food processor, puree half the cauliflower mixture with the butter. Add the remaining cauliflower; puree until smooth. Season; transfer to a bowl.
Wipe out the skillet; melt the remaining 1 tbsp. butter over medium heat. Add the panko; toast until golden, 2 minutes. Sprinkle the puree with the panko.