In a medium-sized bowl add your crawfish, shrimp, and cajun seasoning.
Toss to combine.
Set to the side.
In a medium saute pan add your butter over medium heat and stir until melted.
Add your flour to the butter and mix until combined and it starts to turn a light caramel color. Add your milk to the butter mixture and mix until combined.
Add your cheese and spices to the sauce mixture and stir until melted and combined.
Reduce the heat to low.
In a small saute pan add your shrimp and crawfish stir until heated.
Prepare your fries as directed on the bag.
Place the fries on a parchment-lined baking pan or dish.
Top the fries with the crawfish and shrimp.
Now pour your sauce on top of the fries, making sure to cover most of the fries.
Garnish and enjoy!!