Lobster and caviar gratin served in the shell

Preheat two water baths - one at 50°C and one at 55°C

Bring a large pan of water to the boil and plunge the lobsters into the pan for 30 seconds. Drain the lobsters, then remove the claws and the lower claw joints (still joined together) and place them directly in the water bath at 50°c. Place the joined lobster bodies and tails directly in the water bath at 55°c. Cook all the lobster for 25 minutes

Remove all pieces of lobster from both water baths. Split the lobster bodies and tails lengthways and remove the tail meat, then crack the claws and remove the meat from these too. Cut all the lobster meat into generous chunks and place in the fridge until required, reserving the shells from both the body and claws

Remove the gills from the lobster heads. Choose the four best looking half shells and place in the fridge until required. Put all the remaining shells into a large bowl and crush them with a rolling pin for the lobster bisque

Place a large pan on the hob to heat up. Add the vegetable oil, shallot and pieces of lobster shell. Roast over a high heat until all moisture has evaporated

Add the tomato purée to the pan and cook for 1 minute before adding the brandy. Finally add the cream, peppercorns and tarragon to the pan, bring to the boil and reduce the heat to low. Simmer gently for 15 minutes. Pass the finished bisque through a fine sieve

To prepare the gratin, slowly melt the butter over a low heat and, in a separate pan, gently heat 300ml of the lobster bisque until warm. In a third pan heat water until simmering, placing a bowl with the egg yolk, water and lemon juice over the top. Whisk continuously until the egg mixture becomes thick and glossy. Remove the bowl from the heat and, still whisking continuously, gradually add first the melted butter followed by the bisque. Pass the finished gratin mix through a fine sieve

Place the four empty half lobster shells on a baking tray. Divide the spinach, concasse, tarragon and lobster meat between the four shells. Add a generous amount of gratin mix to each lobster half. Grill under a preheated hot grill until golden and glazed. Dot the caviar over each lobster and serve immediately