Preheat oven to 400 degrees. Heat large sauté pan over medium heat. Add olive oil and leeks to the pan. Sauté until leeks begin to soften and brown; season with 1/4 teaspoon salt. Add carrots and celery to pan, season with 1/4 teaspoon salt; cook for five minutes, stirring occasionally. Stir in fresh corn and sauté for another 2-3 minutes. Transfer mixture to a large baking dish. Set aside.
In same pan, melt butter. Sauté crawfish tails for 2-3 minutes, coating well with the butter. Sprinkle in flour and stir well to coat. Allow to cook for 1 minute. Add vegetable stock, Old Bay seasoning, smoked paprika, pepper and remaining salt; stir well to combine. Bring to a gentle boil. When sauce has thickened, transfer to baking dish with vegetables. Stir well to evenly combine.
Depending on the size and shape of your baking dish, top with pie crust--either whole or cut into strips and laid into a criss-cross pattern. Brush beaten egg over pie crust.
Bake 20-30 minutes or until crust is golden brown. Allow to cool for 10 minutes before serving; filling will be extremely hot.