1 pound lump crabmeat, or 4 large live blue crabs
8 ounces small shrimp
4 tablespoons (1⁄2 stick) butter
1 onion, finely chopped
1 green bell pepper, cored, seeded, and diced
1 red bell pepper, cored, seeded, and diced
4 cloves garlic, minced
2 cups Fish Stock (see page 330) or bottled clam broth
2 cups light cream or half-and-half
1 cup heavy (whipping) cream
Salt and freshly ground black pepper
1⁄4 cup coarsely chopped fresh Italian (flat-leaf) parsley