Peel the shrimp and place the shells into 10 fluid ounces of water and boil for 20 minutes, strain then reduce the liquid to 5 fluid ounces this is the Hot Stock.

Lightly oil 8 small ramekins.

Put 3 tablespoons of the stock and the gelatin into a bowl and stand it in a pan of simmering water, stir until the gelatin has dissolved, then pour it into the bowl of a food processor or blender with the rest of the stock.

Peel and stone the avocados and roughly chop the flesh, add to stock in the processor along with the lemon juice and garlic, blend until smooth.

Put the mixture into a bowl and stir in the yoghurt and mayonnaise, mix thoroughly and season to taste. Spoon the mixture into the oiled ramekins, cover with cling film and chill until set.

When you are ready to serve, slide a palette knife around the edge of each ramekin and ease the mousse away from the sides. Turn the mousses out onto serving plates and top each one with some of the shelled shrimp and drizzle some of the walnut dressing over each mousse.

Serve with crusty bread and a few salad leaves.