Two and a half kilos of potatoes (washed), 50g of porcini mushrooms, olive oil, eight cloves of garlic (peeled and crushed), 25g of butter, some rosemary needles, two tablespoonfuls of olive oil.
Soak the porcini in a litre of tepid water for about an hour. In the meantime, cut the potatoes into thick slices. Don’t peel them. Then fry the garlic in butter and olive oil. Strain the water from the porcini. Don’t discard it. Add the porcini and rosemary to the pot and fry them for a couple of minutes. Pour in the liquid from the porcini and the potatoes to the pot. Bring it to the boil and let it bubble for 15 minutes. Preheat the oven to gas mark 5/190C. Transfer the contents of the pot to an oven-dish, season it with salt and pepper, and bake it for 90 minutes.