Preheat the oven to 350 degrees F (175 degrees C).

Combine macadamia nuts, bread crumbs, 1 teaspoon oil, black pepper, and pepper flakes in the bowl of a food processor; pulse until smooth. Set aside.

Combine mango, cream, and lemon juice in a small saucepan over medium heat; bring to a boil, reduce heat to low, and simmer until thickened.

Season sea bass with salt and black pepper. Heat remaining 3 teaspoons oil and garlic in a large oven-proof skillet over medium heat. Add sea bass; sear on both sides.

Transfer sea bass to the preheated oven; bake until cooked through. Cover sea bass with macadamia crust mixture; return to the oven until crust browns. Top servings with mango cream sauce.