Bring a large pot of salted water to a boil.
Cook the pasta. Add the protein penne and cook according to package directions until al dente.
Drain the pasta and set aside.
Mix the stuffing base. In a mixing bowl, combine the crab cake mix, diced red bell pepper, sliced green onions, mayonnaise, sour cream and egg.
Stir until fully blended into a thick, scoopable mixture. If it's too dry, add a splash of melted butter or extra mayo and sour cream until moist.
Gently fold the crab meat into the stuffing mixture.
Refrigerate the stuffing while you prep the fish, so it firms up.
Pat the catfish fillets dry with paper towels.
Season both sides of each fillet with salt, pepper, garlic salt and creole seasoning.
Lay each fillet flat and spoon a generous portion of stuffing down the center.
Fold or roll each fillet around the stuffing or simply mound the stuffing on top if you plan to broil.
Cook the fish (pan-sear option). Heat the olive oil and butter in a large skillet over medium heat. Cook the stuffed fillets 4-5 minutes per side until golden and the fish flakes easily.
Cook the fish (broil option). Place fillets on a greased baking sheet, drizzle with oil and dot with butter and broil 10-12 minutes until the stuffing is golden and the fish is opaque and flaky (internal temp 145°F).
While the fish cooks, melt the butter (for sauce) in a saucepan over medium heat.
Add the green onions and red bell pepper to the saucepan and sauté for 2-3 minutes until softened.
Pour in the heavy cream and bring to a gentle simmer, do not let it boil.
Reduce heat to low and stir in the shredded cheddar a handful at a time until melted and smooth.
Season the sauce with the garlic salt and Creole seasoning, tasting as you go.
Toss the drained penne with a few spoonfuls of the sauce to coat.
Divide the pasta among plates and place a stuffed fillet on top of each.
Finish and serve. Spoon the remaining sauce generously over the fish. Garnish with extra sliced green onion, if desired, and serve immediately.