In a heavy-duty roasting pan or in a large, deep skillet, heat the oil over moderate heat until hot but not smoking. Add the shells and sear until they turn bright pink, 2 to 3 minutes. Add the orange quarters, fennel seeds, star anise, 4 quarts cold water, the tomatoes, bay leaves, garlic, chile peppers, sea salt, and tomato paste. Bring to a boil, uncovered, and boil vigorously for 30 minutes. To extract the maximum flavor from the shells, use a wooden mallet to crush and break them up while the soup is cooking. Line a large colander with a double layer of dampened cheesecloth, and place the colander over a large bowl. Ladle the broth into the colander, discarding the solids. Taste for seasoning. Serve warm in small cups as an appetizer, or in warmed shallow soup bowls as a first course.
Recipe courtesy of THE PARIS COOKBOOK (HarperCollins, 2001) by Patricia Wells