Start by preparing the pasta dough; sift the flour onto a flat work surface. Add a little salt and create a well in the mound of flour in the centre. Pour in the eggs and egg yolks and use a fork to bring the flour and egg together from the edges of the well.
Once it has begun to be incorporated, use your hands to bring the dough together. Add the olive oil at this point and continue to knead for 10 minutes until smooth, shiny and elastic. Cover with clingfilm and chill for 30 minutes.
Meanwhile, whisk together the sugar, lime juice, sherry vinegar and soy sauce until the sugar has dissolved. Roughly chop the prawns and add to the sauce and add the spring onions too. Cover and chill until needed.
Remove the pasta dough from the fridge and roll into a rectangular shape, thin enough to pass through the thickest setting of a pasta machine. Roll the pasta through the machine to smooth and thin, folding in half to control the size. Continue to decrease the thickness setting until you have reaching the thinnest setting on the machine. Rest the pasta dough on a lightly floured surface and cut in half so you have two identical rectangular sheets of pasta.
Use a 5cm circular cutter to cut out discs of pasta. Arrange teaspoons of the prawn filling in the centre and wet the rim with a little water using your fingertip. Bring the pasta up and around the filling, twisting carefully at the top to secure.
Arrange the ravioli on a lined baking sheet until ready to cook. Arrange in batches in a lined double boiler set over simmering water.
Steam for 10-12 minutes until the pasta and the filling are just cooked. Remove and arrange on serving plates. Serve with small pots of the sweet chilli sauce.