Scrub unpeeled potatoes, add to pot along with enough milk to cover potatoes halfway. Then add enough cream to completely cover the potatoes. Also add peeled/crushed garlic cloves and thyme. Bring to a boil and cook until tender. When potatoes are done, drain them in a colander under which a large bowl has been placed. Place potatoes back into the cooking pot. Mash potatoes. Add cupfuls of the hot milk/cream as you mash, until you reach desired consistency. Add a pat of butter and salt and pepper to taste. Fold in two heaping tablespoons of course-grain mustard. Any leftover milk/cream can be used to "revive" your potatoes in case you end up with late dinner guests or if you have leftovers.