Wash chicken livers under cold running water. Dry well, and season with salt and pepper. Dust chicken livers with flour; set aside.
In a large nonstick saute pan, combine olive oil, onion, sage, chopped garlic, red-pepper flakes, capers, and anchovies. Cook over medium heat, stirring frequently, for 3 minutes. Add chicken livers, one piece at a time. Cook, covered, until evenly browned, about 3 minutes on each side. Add Vin Santo, scraping the brown bits from the bottom of the saute pan. Cook until the wine has reduced by half, 2 to 3 minutes. Stir in tomato, and cook, stirring occasionally, about 6 minutes. (The dish should be slightly soupy. If it starts to become dry, add a little water.) Remove the saute pan from the heat, and stir in parsley.
Rub the toasts with the whole garlic clove. Drizzle with olive oil, and season with black pepper. Spoon the livers over the toasts, and serve immediately.