Add onion, bell pepper, celery, garlic, and green onions into a food processor and blend until finely chopped
Heat oil in a heavy-bottom stock pot. (cast iron preferable)
When oil is hot (medium-high), whisk in flour to make the roux and stir constantly.
Continue stirring until the roux is the color of peanut butter, or for a richer flavor, the color of Nutella. Add in finely chopped vegetables.
Sauté for 5 minutes.
Stir in tomato paste until well combined.
Pour in the reserved crawfish stock, stir, and bring to a simmer.
Add remaining crawfish tails in the liquid crab boil. Add crawfish tails to the pot.
Stir in onion, curry and garlic powders.
Add heavy cream and gently stir.
Reduce heat to low and simmer, uncovered for 20 minutes to thicken.
Add stuffed crawfish heads.
Continue to simmer for 10-20 more minutes.
Taste and adjust seasoning, if needed.
Serve over a warm white-rice dome and garnish with fresh, chopped green onions.