Pulse flour and 3 eggs in a processor until crumbs form, then knead into a dough.
Knead for 3 minutes until elastic, wrap in film, and chill for 20 minutes.
Run dough through the thickest setting of a floured pasta machine.
Repeat rolling through thinner settings 4 times, keeping unused pasta covered.
Halve the lobster, remove meat, and slice into 1cm thick pieces.
Cut 9cm pasta circles, fill with lobster and basil, fold into tortellini shapes, and seal with water.
Fry lobster shells in butter, add vegetables and herbs, flambé with brandy, then simmer with stock and cream.
Blend the sauce in batches until it reaches a fine purée consistency.
Boil tortellini for 2 minutes in salted water, drain, and toss in the sauce.
Blanch samphire for 2 minutes, sauté in butter, and serve topped with pasta, sauce, tomatoes, and chives.