Soak corn husks in hot water about 30 minutes or until softened. Drain and pat dry.
Place masa in a large bowl, and gradually add chicken broth; knead until smooth. Stir in baking powder and corn oil.
Place 1 large or 2 small, overlapping corn husks open on a work surface. Spread 2 tablespoons masa mixture in center, leaving about 2 inches bare at top and bottom.
Layer 1 prawn, 1 pepper strip, 1/2 tablespoon each cheddar and Jack cheese, and 1 tablespoon spinach in center. Fold over sides, and then fold up the top and bottom. Tie with string or strip of corn husk to secure. Repeat with remaining husks.
Fill a steamer basket with tamales, upright in layers. Cook over simmering water 60 to 90 minutes, replenishing water as needed, until the husk just pulls away from the masa without sticking.
Open corn husk, and top tamale with Cilantro-Lime Cream Sauce. Garnish, if desired.