Select a heavy skillet large enough to hold 6 ostrich fillets in a single layer without touching and place over medium-high to high heat. Add 1/2 tablespoon unsalted butter and 1 tablespoon olive or canola oil. When foam subsides, add 6 ostrich fillets and saut� quickly, turning once, until nicely browned on both sides and rare in center, 1 to 2 minutes on each side. Sprinkle with coarse sea salt and freshly ground black pepper as you turn fillets over and be careful not to overcook. Test as directed. Transfer fillets to a heated platter and keep warm. Lower heat to medium, then add 3 tablespoons minced shallots to skillet. Cook, stirring, 2 minutes. Raise heat to high and add 1/2 cup brandy, stirring up any browned bits on skillet bottom. Cook until liquid is reduced to about 1/3 cup. Swirl in 1/2 tablespoon unsalted butter and pour over fillets. Sprinkle with minced fresh cilantro and serve immediately.