You need 1 ingredient. The key ingredients include: ["For the truffled polenta croutons:", "3/4 cup medium fine stoneground cornmeal", "3 1/4 cups water", "1/2 teaspoon salt", "1/4 cup fresh grated parmesan cheese", "2 tablespoons white or black truffle oil", "1 tablespoon unsalted butter", "For the soup:", "4 ounces piece of trimmed leek, halved lengthwise, thickly sliced so they don't disintegrate completely, rinsed and shaken dry", "1 spring onion bulb or 2 scallions, roots trimmed, chopped", "1 green garlic bulb or 1 fat garlic clove, chopped", "4 ounces trimmed fennel bulb, halved lengthwise, sliced about 1/8"" thick", "1 tablespoon olive oil", "1 2"" serrano pepper with seeds, minced", "1 quart broth from cooked beans (see note)", "2 cups chicken or vegetable broth", "1 packed cup loosely chopped cleaned cilantro leaves and tender stems, plus a bit more for the garnish", "1/2 cup packed loosely chopped cleaned flat leaf parsley leaves, plus a bit more for the garnish", "2 cups cooked cranberry or borlotti beans (see note)", "1 or two bunches swiss chard, (you'll need a packed quart of leaves) rinsed, leaves cut into ribbons, stems chopped into 1/2"" pieces (keep stems separate)", "salt to taste", "extra virgin olive oil for the garnish", "the rind of one preserved lemon (regular or meyer is okay)"].