Cut out 16 squares of aluminum foil measuring 6½ inches (16.2 cm). Set a cake ring, 3 inches (7.5 cm) in diameter and 2 inches (5 cm) tall in the center of each square. Fold and pleat the edges of the foil up around the rings to make a tight seal. Because the cakes will be baked in a water bath, be certain that the foil reaches at least three-quarters of the way up the s