Start by making a roux. In a heavy bottom pan, add vegetable oil, butter and flour. Cook over low heat, stirring often.

Cook until roux is a dark peanut butter color, about 30 minutes, stirring continually. Keep a watch at all times, it is easy to burn the roux.

Add onions, peppers and celery with olive oil to a skillet and cook over medium heat until vegetables start to soften. Season with garlic, salt, black and red pepper. 

Mix in mushrooms and continue to cook until softened.

In a dutch, add the seafood stock with 1 cup of the roux, vegetables and blackened seasoning. 

Cook over medium heat until mixture just comes to a boil and starts to thicken.

Add additional roux if mixture seems too thin or add a bit more broth if it seems too thick. Remaining roux can be refrigerated or frozen for another use.

Lower filling to simmer, stir in cream. 

Stir in crawfish tails. Remove from heat. 

Place pie crust into a deep dish pie plate. 

Pour in filling. 

Top with remaining pie crust, trimming the edges. 

Use a fork to crimp the edges, pressing the layers of pie crust together. Cut vent holes into the pie crust with a sharp knife. 

Place pie onto a baking sheet to catch any spills in the oven. 

Bake for 45 minutes or until pie crust is golden brown. If pie crust starts to brown too quickly, loosely cover with foil.

Remove from oven and cool about 15 minutes before serving.