In a large Dutch oven or heavy-bottomed saucepan, combine melted butter, oil, and flour until smooth.
Cook on medium heat, stirring continuously, for about 10-12 minutes until you have achieved the desired color. Don’t walk away from the stove during this process. It might burn.
Add the onion, green pepper, and celery and cook for 8- 10 minutes –stirring frequently.
Then add garlic, thyme, and bay leaf – continue stirring for about 2 minutes.
Next, throw in about 1 cup chopped tomatoes, Worcestershire sauce, paprika, and Creole seasoning, and let it cook for 5 minutes.
Gradually pour in about 1 -2 cups of stock bring to a boil, and let it simmer.(adjust thickness with more stock as needed). Add the crawfish, simmer for 3-4 more minutes.
Adjust thickness soup and flavor with more crawfish broth or water, hot sauce, and salt.
Stir in the green onions and chopped parsley.
Serve over hot cooked rice.

Add a teaspoon or two of butter or oil to a saucepan or skillet. Then throw in the crawfish shells, the remaining scraps of onion, garlic, and celery together with aromatics like bay leaf and thyme.
Saute for about 5-7 minutes, constantly stirring to prevent it from burning. Add about 5 cups of water.
Bring to a boil, lower heat, and let it simmer for 20 minutes.
Remove from heat and strain using a sieve. Set stock aside.

Recipe courtesy of African (Immaculate) Bites
https://www.africanbites.com/crawfish-etouffee/

Crawfish Recipes