Preheat oven to 375F.

Bring a large dutch oven filled with water and salt to a boil. Add diced potatoes and boil until fork tender and breaking apart. Drain. Add drained potatoes back into pot.

Add cream cheese, butter, sour cream, milk, garlic, salt, pepper, and thyme. Using a potato masher, mash together all ingredients  until most chunks are gone.

Pour into a 9x13 casserole dish, add butter cubes to the top, and bake for 60 minutes. Let set at least 30 minutes before serving!