Pluck the herb leaves from the twigs and chop finely. Press the garlic. Knead the herbs and garlic with the butter. Loosen the skin of the duck thighs in one place, creating a pocket.
Do not peel off the skin completely. Now spread the herb butter evenly in the thigh pockets. Now salt and pepper the outside of the thighs well and place them skin side down in a very lightly oiled baking dish.
Fill an oven-proof dish with 1 liter of water and place it in the oven. This will keep the thighs even juicier. Cook the legs in the oven for one hour at 160 °C (top/bottom heat). Then turn the thighs over and cook in the oven for another hour.
During the entire cooking time, keep pouring the escaping juices over the thighs.