For the pasta, place all the pasta ingredients into a food processor and pulse until the mixture just comes together to form a dough.
Turn out the dough onto a floured work surface and knead until smooth, then pass through a pasta machine 5-6 times, decreasing the thickness setting every time, until you have a smooth, thin sheet of pasta.
Cut the pasta sheet into two pieces 5cm/2in x 5cm/2in.
Cook the pasta squares for 2-3 minutes in boiling salted water. Remove with a slotted spoon and place onto a plate.
For the filling, fry the prawns and garlic in one tablespoon of the olive oil for 3-4 minutes, or until the prawns are cooked through, then set aside.
Place the tomato ketchup, Worcestershire sauce and Tabasco sauce into a pan over a low heat and stir well, then add the tarragon and chervil.
To serve, place a cooked pasta square on the centre of a plate. Place the prawns into the middle and spoon the sauce over the prawns. Place the second piece of pasta over the top and spoon over a little more sauce.