Season the fish with salt and pepper and place on a large plate; spread 1 1/2 tbsp. mustard evenly on top of each piece. Sprinkle the breadcrumbs over the mustard, pressing to adhere. Refrigerate while you make the creamed corn.
Using a food processor, puree 3 cups corn kernels. Transfer to a small saucepan and stir in the remaining 1 cup kernels. Add the butter and cook over medium heat until hot, about 5 minutes. Stir in the cream and cook, stirring occasionally, until slightly thickened, about 5 minutes. Season with salt and pepper. Remove from the heat and cover to keep warm.
In a nonstick skillet, heat 2 tbsp. EVOO over medium-high heat. Add 2 pieces of fish crumb side down, reduce the heat to medium and cook, turning once, until golden and crisp, about 8 minutes. Repeat with the remaining 2 tbsp. EVOO and fish.
Serve the fish on a bed of the creamed corn. Sprinkle with the parsley and serve with the tomato wedges. Season with pepper.