This chicken-liver mousse with pickled red onion is a creamy and flavorful appetizer that is perfect for entertaining. The mousse is made by blending cooked chicken livers with butter, cream, and seasonings until smooth and velvety. The pickled red onion adds a tangy and slightly sweet flavor that complements the richness of the mousse. Serve this delicious spread on toasted baguette slices or crackers for a sophisticated and impressive appetizer.