Brush the inside of four ramekins or dariole moulds with melted butter and place in the fridge. In a deep-sided frying pan or a saucepan bring 3 inches of water to a gentle simmer.
To make the mousse, place the raw rabbit and the egg white into a food processor and pulse until smooth. Gently add the double cream, mixing all the time. Place the mix into a bowl and add the cooked rabbit, tarragon and seasoning. Mix well and place into a piping bag. Pipe the mix into buttered moulds, cover with the tin foil and place on a trivet in the simmering water for 10-12 minutes, or until the mousse is springy to the touch or the core temperature has reached 65c. Remove from the water and keep warm.
For the sauce, bring the sherry to a boil and let it reduce by one third. Add the stock and repeat the process. Finish by stirring in the double cream and chopped parsley.
Toast the baguette in a char-grill pan brushed with a little oil or under the grill
To serve, turn out the mousse onto a warm plate, drizzle all over with the sauce, and garnish with parsley and the crispy baguette. To add a retro feel, you can cut the bread into rabbit shapes!