Heat a little of the butter in a large frying pan over medium heat until the butter has melted and is foaming. Add the minced shallots and cook until they are softened and translucent. Turn the heat up and add the chopped livers. Cook for 3 minutes, turning with a spatula; do not worry if the centers are a little pink. Make sure you don't overcook.
Put into blender or food processor. Add the thyme, Vegeta, black pepper, cream, softened butter, and blitz until super-smooth.
Using a fine sieve, push the liver mousse through the remove any lumps or remaining bits of connective tissue into a bowl. Using a wooden spoon whip the mousse once again and now it will be light and airy and exceedingly smooth.