Sear the Shrimp. Melt butter and sauté garlic for 30 seconds. Add shrimp; sear for 60 seconds (do not fully cook). Remove and set aside.
Sauté Aromatics. In the same skillet, cook onion, celery, and bell pepper until translucent.
Whisk the Roux. Add broth and half-and-half. Add spices. Sprinkle flour over the top; whisk constantly for 2 minutes until it reaches a thicker consistency.
Combine. In a baking dish add cooked rice, seared shrimp and the roux sauce. Stir until the grains are evenly coated.
Bake. Bake at 400°F for 15 minutes. Top with cheese and bake for 5 more minutes until bubbly.
Serve. Let everything rest for 5 to 10 minutes, then top with diced scallions or parsley (option), then serve.
Video
Notes
Make sure you sear it for only 60 seconds and pull out the baking dish as soon as the shrimp looks juicy, pink and opaque.
Use rice that has cooled down completely or been cooked the day before and refrigerated.
If the sauce seems too thick, add some more broth to adjust its consistency.
Always let the casserole rest for a few minutes after it is out of the oven.