Peel the pumpkin, scoop out the seeds and then cut the flesh into small cubes. Peel and finely dice the shallot.
Heat a large saucepan and add a drizzle of olive oil. Sweat the shallots with a pinch of salt for 1 minute then add the pumpkin cubes and the sprig of thyme. Cook for 5 minutes, stirring often. Add enough water to cover the pumpkin, cover with a lid and cook for 15 to 20 minutes. Remove the thyme sprigs and add the cream. Bring back to the boil then blend until smooth. Adjust the seasoning, set aside and keep warm.
Place the sea urchins and the cream in a blender and blitz until smooth. Adjust the seasoning and then pour the liquid into a syphon. Attach the gas canister and then chill.
Remove the head and the shell, leaving the tail intact. Use the tip of a sharp knife to remove the black spine.
Heat a frying pan to hot and add a dash of olive oil. Cook the langoustines for 1 minute on each side. Remove from the pan and set aside on a few sheets of kitchen towel. Season with salt and pepper.
Serve the pumpkin velouté and top with 3 langoustines per portion. Finish with a little of the emulsion and add a few sprigs of fresh coriander.
«If you cannot get hold of sea urchins, use a bisque in the emulsion instead. Make a bisque using the langoustine heads. The best time to eat langoustines is between April and October - make this recipe using prawns or scallops outside of this season.»