4: Put 2 tablespoons goose fat into a large saucepan on high heat. When good and hot, add the mushrooms. Sauté for a few minutes until lightly browned. Salt and pepper only after cooking. Set aside.
5: Use the same pan, still on high heat. Pour in 4 tablespoons olive oil and when hot, add the shallots. Salt and pepper, then cook fro 1 minute without colouring.
6: Add the chopped leeks and mix well. Cook until the leeks are just tender, but still nice and green (about 3 or 4 minutes). Preheat the oven to 360°F (180°C).