Clean the leeks, rinse and cut the stalks in half lengthwise. Rinse the flesh, dry it. Peel garlic and cut into sticks. Lard the roast with it. To do this, pierce a pointed kitchen knife into the meat and push 1 garlic stick into each along the edge.
Season meat all over with salt, pepper and thyme. Brown in one third of the fat on all sides, remove again.
Melt remaining fat in saucepan and sauté leeks over medium heat. Season with nutmeg. Place meat on top and steam with lid closed for 1 1/2 hours.
Cut roast into slices, season roast stock with salt and freshly ground pepper to taste.
Tip: Instead of clarified butter, you can also use butter in most cases.