Shrimp:

• 1 1/4 pounds large peeled and deveined uncooked shrimp (21-30 count) tails removed
• Salt and freshly ground black pepper

Rice and Vegetable Mixture:

• 6 tablespoons butter, divided
• 1 medium onion, finely chopped
• 2 stalks celery, chopped
• 1 medium red bell pepper, finely chopped
• 3 cups water
• 1 1/2 cups white long-grain rice, preferably converted or parboiled rice
• 1 can (5-ounce) whole water chestnuts, halved lengthwise and cut into 1/4-inch pieces

Sauce:

• 1 cup half and half
• 1/2 cup mayonnaise, preferably full-fat
• 1/4 cup tomato puree
• 1 tablespoon lemon juice
• 1 teaspoon paprika
• 1/2 teaspoon cayenne pepper, or to tolerance
• 1/4 teaspoon ground nutmeg
• 1/4 cup chopped fresh parsley, divided

Additional Ingredients:

• 1 container (8-ounce) jumbo lump crab, drained, rinsed, and picked over for any shell fragments
• 1 1/2 cups coarse fresh breadcrumbs