This meaty taste of ostrich — best served rare, since it is so lean — takes well to the crunchy, flavorful sweet potato croquettes. Panko, irregularly shaped Japanese breadcrumbs, give the croquettes an extra-crispy crust. Layers of mustard and berry flavors blend into a mouthwatering sauce. Serve with thinly sliced red cabbage sautéed until tender in a mixture of olive and hazelnut oils, seasoned with cumin seeds, salt, and pepper.
When the sweet potatoes are cool enough to handle, scoop out the flesh and transfer to a nonstick skillet. Cook over medium heat until very dry, turning occasionally, and breaking up with a wooden spatula.
Let cool, then stir in the hazelnuts and sage, and season with salt and pepper, to taste. Form into four 1-inch-thick round cakes. In a bowl, beat the eggs with the milk to form an egg wash. Dust the cakes with flour, drop into the egg wash, then cover with breadcrumbs. Set aside on a rack.
Heat 1 teaspoon of the oil in a skillet over medium heat. Add the shallot and cook until softened, 2-3 minutes. Stir in the marmalade and cracked pepper. Pour in the vinegar, increase the heat to high, and boil until the liquid has almost evaporated.
Stir in the stock, then the mustard, and gently boil until reduced to the consistency of a thin sauce. Keep warm.
Season the ostrich with salt and pepper, to taste. Heat 3 teaspoons olive oil in a large skillet over high heat until hot. Add the ostrich and cook quickly on both sides until browned and rare or medium-rare, turning once. Remove from the pan and keep warm.
Pour enough olive oil into a skillet to measure about ½-inch deep, and heat over medium-high heat until hot. Add the croquettes and cook until golden brown on one side, turn with a spatula, and cook the second side until brown. Remove, blot dry on paper towels, and keep warm.
Place the croquettes on 4 warmed plates. Lay the ostrich fillets on top. Strain the berry sauce into a clean pan, stir in butter, and season with salt and pepper, to taste. Pour over the ostrich and serve at once.