Place potatoes into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 20 minutes. Drain and mash.
Meanwhile, melt butter in a skillet over low heat and cook garlic until lightly browned, 2 to 3 minutes. Add garlic and butter to the mashed potatoes. Stir in until well combined.
Add creme fraiche and mix until well combined. Mashed potatoes should still be hot. If mashed potatoes have gotten too cold, quickly heat them over low heat on the stove. Mix in cheese until melted and season with salt and pepper.