Preheat the oven to 180 degrees C. Arrange the French bread on a baking tray. Using 1 tablespoon of the oil, lightly brush the slices of bread on the top side, then bake for 10 minutes or until golden brown.
Meanwhile, heat the remaining 1 tablespoon of oil in a heavy-based frying pan. Add the onion and garlic and sauté over a medium–high heat for 2–3 minutes or until softened.
Add the chicken livers and mushrooms and cook, stirring constantly, to brown on all sides. Add a little hot water if the livers begin to stick to the pan. As they cook, break up any large livers into bite-sized pieces, using the side of the spatula.
Add the balsamic vinegar, shredded sage and seasoning to taste. Reduce the heat a little and continue cooking for 5–10 minutes or until the livers are just cooked through.
Serve the chicken livers on top of the baked French bread rounds, garnished with sprigs of fresh sage.