| 3 tablespoons vegetable oil |
| 2 cups sliced onions; large Bermuda or Spanish |
| 2-1/2 cups sliced leeks, about 3, cleaned thoroughly |
| 1 tablespoon fresh marjoram, chopped, or 1-1/2 teaspoons dried |
| 8 cups peeled, sliced potatoes, approximately 4 pounds |
| 3/4 cup buttermilk or plain low-fat yogurt |
| 1/2 teaspoon freshly ground black pepper, or to taste |
| Pinch of ground cardamom (optional) |
| 1/2 pound fresh mushrooms, sliced |
| 1 tablespoon vegetable oil |
| 1/2 cup peeled, diced carrots, precooked |
| 1 cup peeled, diced potatoes, precooked |