
Continue cooking for 1 minute, stirring all the time. Stir with a wooden spoon until a paste forms. Put over a medium heat and once the butter has melted, add the flour. Wipe out the pan and add the butter, cayenne pepper and mustard powder.
Preheat the oven to gas 6, 200☌, fan 180☌.
Cook the pasta in a large pan of boiling water following the packet instructions. Pour in the milk and bring up to the boil, then turn off the heat and leave to cool and infuse for 20 minutes, then strain into a jug, discarding the shells and seasonings. Put the onion halves, bay leaves, garlic and peppercorns into a medium pan with the shells from the lobster tail and the cracked legs. (Reserve the tail and leg shells from both lobsters.) Chop all the lobster meat and set aside in the fridge until needed. Discard the dark stomach sack and use a pick or skewer to extract the meat from the legs.
Arch the back of the lobster until it cracks to remove the tail, bend flat and break off the shell to extract the meat. Remove the lobsters claws by twisting them off the body, crack with a nutcracker or a small hammer to break the shell and remove the flesh.