Preheat oven to 350 degrees. Lightly coat the bottom of a 7 and a 1/2 cup baking dish with 1 Tablespoon of olive oil.
Place catfish fillets in the baking dish, arranging them so they do not over lap. Pour wine over the fish, and sprinkle with dill.
Cover with foil, and bake for 20 minutes, or until fish starts to flake apart.
While fish is cooking, saute the mushrooms in 1 Tablespoon of olive oil. Remove from pan and set aside.
Add 1 Tablespoon of oil to the same pan, and cook shrimp until no longer pink.
Remove fish from the oven, and carefully pour liquid into a measuring cup or bowl. Set aside.
Increase the oven temperature to 425 degrees.
Scatter the mushrooms and shrimp over the fish, and set aside.
Heat 4 Tablespoons of butter in a pan over medium-low heat until melted. Stir in the flour, and cook for 2 minutes without browning.
Stir the reserved cooking liquid into the roux. Bring to a boil while continually stirring to create a smooth sauce.
Add the coconut milk/heavy cream and season with salt and pepper.
Pour sauce over fish, and smooth to cover completely.
Drain the cooked potatoes, and mash or beat with a mixer until smooth. Add 2 Tablespoons of butter, salt and pepper, and stir until melted.
Carefully spread the mashed potatoes over the fish mixture, and smooth the surface to cover the surface completely.
Bake for 10 to 15 minutes until golden brown.
Remove from oven and allow to cool for 5 to 10 minutes before serving.