Put a large saucepan of salted water on to boil. Heat a large nonstick frying pan to a high heat and brush it with the olive oil. Sear the lamb for 1-2 minutes until browned all over. Transfer it to a plate, sprinkle the sesame oil over it and keep it warm.
Put the pasta in the boiling water and cook according to the instructions on the packet.
Drain the pasta and toss it with the coriander and parsley, chillies, garlic, lime juice, a pinch of salt and plenty of freshly ground black pepper. Add a dash of spicy sauce, if using, and a few extra drops of sesame oil if liked.
Arrange a mound of the spiced pasta on each plate and top with the slices of lamb.
Lamb fillet is so tender it can be seared briefly over a high heat, using hardly any fat.