How to Make It
In a large skillet, melt 2 tablespoons of the butter over moderate heat. Add the onion and garlic and cook, stirring occasionally, until lightly browned, about 10 minutes. Transfer the onion and garlic to a food processor. Melt the remaining 2 tablespoons of butter in the same skillet. Add the chicken livers, season with salt and 1/2 teaspoon of quatre-épices and cook over high heat until nicely browned on the outside and still pink inside, about 5 minutes. Transfer the livers to the food processor.
Add the Cognac to the skillet and simmer over high heat until reduced by one-third, scraping up the browned bits from the bottom, about 3 minutes. Add the Cognac to the processor and puree until smooth. Season generously with salt and quatre-épices. Pack the pâté into a small bowl, press a piece of plastic directly on the pâté and refrigerate until firm, at least 2 hours or for up to 3 days. Bring to room temperature before serving.
Preheat the oven to 350°. Brush the baguette slices on both sides with olive oil and arrange on a baking sheet. Sprinkle the bread liberally with salt and bake for 10 minutes, or until golden brown and crisp. Serve the pâté with the toast.