Melt the butter. Grease the hollows of a muffin tray (12 hollows) well. Cut out 12 circles from baking paper the size of the muffin bottoms and place them in the recesses. Wash the potatoes thoroughly and cut or slice them very thinly.
Place in a bowl and season with salt and pepper. Pour remaining butter over it and mix well.
Wash the thyme, shake dry and, except for something to garnish, remove leaves from the stalks. Place a few leaves of thyme in each hollow of the muffin tray. Mix the remaining leaves under the potato slices.
Spread the potato slices in the wells and drizzle the rest of the butter from the bowl over them. Close the muffin tin with aluminium foil. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see
manufacturer) Bake for 15-20 minutes. Take out and carefully turn over, remove baking paper. Arrange on a plate and garnish with remaining thyme.