In a 6-quart pot, combine potatoes, cauliflower, roasted garlic, Holland House White Cooking Wine, stock, heavy cream, thyme, and salt and simmer for 15 to 20 minutes or until potatoes are just cooked through.
Remove from heat. With a potato ricer or food mill, mash potato and cauliflower mixture until smooth. While still hot, mix in Parmesan cheese, Asiago cheese, and butter. Season to taste with black pepper.