Preheat the oven to 350 degrees F. Set the baguette slices on a baking sheet and lightly brush with the olive oil. Bake until light brown on both sides, turning once, about 4 minutes. Alternately the bread may be browned on a grill, which will impart a light smoky flavor.

In a large skillet melt the bacon fat over medium high heat, add the onion and saute until soft, about 3 minutes. Add the chicken livers, Cognac and sage to the pan and saute until the livers are browned on all sides but still slightly pink in the center. Stir in the capers and season, to taste, with salt and pepper.

Transfer the chicken liver mixture to a food processor and puree on high speed. Allow to cool before spreading on the crostini