Lobster mousse

1.Kill lobster humanely (see note), then remove tail meat by running your finger along the connective tissue between the shell and meat. Refrigerate meat until required. Chop or crush shells, then place in a large saucepan over medium heat with shallot, thyme and 100gm butter, and stir and pound shells with the end of a rolling pin to break up until shells are fragrant and deep red (20-30 minutes). Add flour and stir until well combined and toasted (3-4 minutes). Add tomato paste and stir continuously until it loses its raw flavour (1-2 minutes), then deglaze pan with Cognac and gradually add stock, stirring until smooth. Increase heat to high and stir until liquid comes to the boil, then stir occasionally until well flavoured (2 minutes). Remove from heat and strain through a sieve, pressing to extract the most liquid, then strain again through a fine sieve; you should have 300ml. Return to pan and bring to a simmer. Squeeze excess water from gelatine and stir into sauce to dissolve. Season to taste, transfer to a bowl and set aside, stirring occasionally, until cool (30-35 minutes). Whisk cream to soft peaks, fold into sauce a third at a time, then divide among two 350ml moulds, or one 700ml mould and refrigerate overnight to set.

2.To make Melba toasts, preheat oven to 175C. Cut crusts off bread with a serrated knife, cut slices diagonally in half and bake on trays, turning once, until light golden and crisp (8-10 minutes). Halve toasts again, brush lightly with oil, then return to oven and bake, turning once, until golden (5-7 minutes).

3.Dice reserved lobster meat. Heat remaining butter in a frying pan over high heat, add lobster and stir until just cooked (3-4 minutes). Season to taste and set aside to cool briefly (5-6 minutes).

4.Meanwhile, dip bases of mousse moulds briefly in hot water to loosen, then invert onto serving plates. Spoon lobster meat on each mousse, top with roe and chervil and serve with Melba toasts.