How to Make It
In a medium bowl, cover the livers with the milk and refrigerate for 1 hour.
In a large skillet, heat the olive oil. Add the apple, shallot, garlic, sage, cinnamon, pepper and 1 teaspoon of the salt and cook over moderate heat until the shallot is softened, about 4 minutes. Drain the turkey livers and pat dry. Add them to the skillet and cook until just pink inside, 5 to 7 minutes. Add the bourbon and simmer for 1 minute.
Transfer the contents of the skillet to a food processor. Add the cream and the remaining 1 teaspoon of salt and puree until smooth. Scrape the mousse into a small bowl and refrigerate until firm enough to spread, at least 4 hours.
In a small saucepan, combine the sugar with the vinegar and simmer over moderate heat until the sugar dissolves. Add the shallots, salt, pepper and thyme and simmer over moderately low heat, stirring occasionally, until the shallots are softened, about 8 minutes. Remove from the heat and let the shallots pickle for 10 minutes. Using a slotted spoon, remove the shallots from the brine and spread on a plate to cool. Discard the thyme sprig. Transfer to a bowl for serving.
Preheat the oven to 350°. Spread the baguette slices on baking sheets and toast for about 7 minutes per side, or until lightly browned. Serve the mousse with the toasts and the pickled shallots.