Cook the pasta and drain.
Measure out seasonings and Worcestershire sauce and set aside.
Preheat oven 350 degrees.
In a 4 quart Dutch-oven, melt butter. Add white parts of the onions and cook down for about 4-5 minutes until onions soften. Stirring occasionally.
Stir in the flour, Old Bay, Worcestershire, mustard, garlic powder, Cajun seasoning, salt, . Cook over low heat stirring constantly until smooth.
Add in the milk and heat until bubbling, stirring constantly.
Once bubbling, remove from heat immediately.
Stir in cheddar, Monterery jack and cream cheese until melted. Then stir in crawfish until evenly distributed.
Add pasta to the mixture and stir until combined.
Bake for 20 minutes, until heated through.
Remove from oven and let it stand for about 10 minutes.
Garnish with green onions and serve.