Coat a box mould (approx. 25 cm long) with oil. Line the mould with 2-3 sheets of aluminium foil (approx. 34 cm long) so that 6-7 cm protrude at each side. Press on the foil, smooth it down and spread with oil. Line the mould with ham slices so that they protrude 5-6 cm. Peel garlic, chop finely, mix with cream and season with salt and pepper.
Grate cheese. Wash the herbs, shake dry and, except for some thyme for garnishing, pluck the leaves from the stalks and chop them. Peel potatoes and slice them very thinly. Layer 2 layers of potato slices in the form like roof tiles, sprinkle with cheese and herbs and pour some cream over them. Repeat the process until all ingredients are used up. Fold the protruding ham slices over the potatoes towards the middle and cover with aluminium foil. Cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) on the second rack from the bottom for 1 - 1 1/4 hours (stick test). Remove the terrine and let it cool down on a cake rack. Remove the upper aluminium foil from the terrine.
Fold the protruding ham slices over the potatoes towards the middle and cover with aluminium foil. Cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) on the second rack from the bottom for 1 - 1 1/4 hours (stick test). Remove the terrine and let it cool down on a cake rack. Remove the upper aluminium foil from the terrine. Pull the terrine out of the mould using the aluminium foil (if necessary, use a sharp knife to remove it from the mould) and turn it over onto a board. Remove all the aluminium foil, arrange the terrine on a plate and garnish with thyme.
waiting time approx. 3 hours