Mix breadcrumbs, garlic, half the zest, 1 tablespoon parsley and a pinch of salt in a bowl.
Heat 2 tablespoons butter in a small sauté pan over moderate heat. Add the crumbs and toast. Stir mixture and cook for about 2 minutes or until golden. Remove from the heat and set aside to garnish the fish after it is cooked.
Heat the remaining 2 tablespoons butter in a sauté pan over medium heat. Heat the remaining 2 tablespoons butter in a sauté pan over medium heat.
Mix the flour, cornmeal, the remaining zest, and 1 teaspoon of salt on a plate. Dredge the fish fillets in the mixture and shake off the excess.
Pan-fry the fillets about 3 minutes per side until crisp and golden. Set aside and keep warm.
Deglaze the pan with the orange juice. Pour sauce around the fish, but not over the top. Sprinkle the toasted crumbs on top of the fillets.
Peel the sweet potato and cut it into quarters. Julienne the quarters lengthwise on a mandolin. Cover with water and place in the fridge for at least 1 hour.
Heat the vegetable oil in a large stockpot to 365 degrees F.
Remove the sweet potatoes from the fridge. Drain and thoroughly dry the potatoes. Toss them in a dry bowl with the cornstarch. Fry the potatoes in small batches 2 to 3 minutes until crisp and golden. Drain on paper towels.
Mix the garlic, orange zest, and egg yolks on high in the small bowl of a food processor until mixture thickens slightly.
Add lemon juice, curry powder and salt.
With the processor on high, slowly drizzle in the olive oil. Continue to mix on high until mixture thickens to a consistency of mayonnaise. Refrigerate until ready to use. Serve with Pan-Fried Orange Roughy and Sweet Potato Frites.