How to Make It
In a medium bowl, cover the livers with the milk and refrigerate for at least 5 hours or overnight.
In a small saucepan, combine the prunes with the red wine, orange juice, lemon juice and sugar and simmer, stirring occasionally, until the liquid has reduced to a thick syrup, about 6 minutes. Let cool and refrigerate.
In another small saucepan, heat 1 tablespoon of the oil over moderate heat. Add the onion and garlic and cook until softened, about 4 minutes.
Drain the livers, pat dry with paper towels and season with salt and pepper. In a large, heavy skillet, heat the remaining 3 tablespoons of oil until shimmering. Add the livers and cook over high heat until well browned, about 1 minute per side. Add the onion-garlic mixture, along with the honey and 1/4 cup of the brandy and light carefully with a long match. Cook the livers until the flames die out and the brandy has reduced to a glaze, about 3 minutes.
Scrape the hot livers into a food processor. Add the cream and blend until smooth. Blend in the remaining 1 tablespoon of brandy and season with salt and pepper. Strain the liver mousse through a fine sieve into a medium bowl. Pack the mousse into a serving bowl and press plastic wrap directly onto the surface. Refrigerate for at least 4 hours or overnight. Serve the liver mousse with the toasts and prunes.