Divide crawfish tail meat into two portions: 1 pound for boulettes and 1.5 pounds for the bisque. Finely chop the 1 pound portion for the boulettes. Dice the onion, celery, and bell pepper for the bisque, and mince them separately for the boulettes. Mince garlic and set aside in two bowls. Slice green onions and chop parsley.
In a large mixing bowl, combine finely chopped crawfish, breadcrumbs, beaten eggs, minced onion, celery, bell pepper, garlic, parsley, Creole seasoning, cayenne pepper, salt, and black pepper. Mix until it holds together. Cover and refrigerate for at least 20 minutes to firm up.
Scoop chilled mixture into tablespoon-sized portions and roll into balls. Dredge each boulette lightly in flour. To fry: heat oil in a skillet over medium heat and cook for 3-4 minutes per side until golden brown. To bake: place on a lined baking sheet, mist with cooking spray, and bake at 375°F for 18-20 minutes, turning once. Set aside.
Melt butter in a Dutch oven over medium heat. Whisk in flour a little at a time until smooth. Reduce heat slightly and stir constantly with a wooden spoon for 20-25 minutes until the roux turns a deep reddish brown, like milk chocolate. Watch closely near the end.
Add diced onion, celery, and bell pepper to the hot roux and cook, stirring often, for 5-6 minutes until softened. Stir in minced garlic and tomato paste and cook for 1 more minute. Slowly pour in the stock while whisking constantly to prevent lumps. Add bay leaf, Creole seasoning, and cayenne pepper. Bring to a gentle boil.
Reduce heat to low and simmer uncovered for 20 minutes. Gently lower the cooked boulettes into the bisque and simmer for another 20-25 minutes, stirring occasionally. The bisque should thicken and coat the back of a spoon.
Stir in the remaining 1.5 pounds of crawfish tail meat and cook for 5-7 minutes to warm through. Remove and discard the bay leaf. Stir in sliced green onions and chopped parsley. Taste and adjust salt, black pepper, and cayenne pepper as needed.
Spoon cooked white rice into each bowl. Ladle the hot bisque generously over the rice, making sure each bowl gets a few boulettes. Garnish with extra green onions or parsley if desired. Serve immediately.