Pulse flour, egg, yolks, and semolina in a food processor until a dough forms.
Rest the dough in the fridge for 30 minutes, covered in cling film.
Roll dough through a pasta machine until the thinnest setting is reached.
Mix crab meats with lemon juice and season with salt and pepper.
Stamp out 6-8cm discs from the pasta sheets on a floured surface.
Place crab mixture on discs, brush edges with egg, and seal into crescent shapes.
Twist crescent edges together to form tortellini and cover until ready to cook.
Clean shellfish and discard any that do not close when tapped.
Steam mussels and clams in wine and coriander stalks for 2-3 minutes until open.
Strain the liquor and shell half of the mussels and clams.
Fry shallots, ginger, and lemongrass in 75g butter for 5 minutes.
Add shellfish liquor and fish stock, boil, then simmer for 4 minutes.
Sieve the liquid into a clean pan and whisk in cream, seasoning, and lemon juice.
Wilt spinach in 50g butter in a sauté pan for 1-2 minutes.
Boil tortellini in salted water for 1-2 minutes until they float.
Serve tortellini over spinach, topped with sauce and garnished with shellfish and cress.