1tspshichimi togarashioptional - this is actually a Japanese seasoning blend (I use it in my Firecracker chicken) - it's a kind of savoury, umami taste. It adds a little extra flavour and looks pretty sprinkled on top.
Place the lamb cutlets in a large bowl and add the gochujang paste, rice wine vinegar, sugar, soy sauce, mirin, ginger, garlic and sesame oil. Mix everything together and cover the bowl with clingfilm. Place in the fridge to marinate for 2 hours (or as long as 12 hours). If you're short on time, even 30 minutes of marinating will still taste great (if you're marinating for 30 mins, there's no need to refrigerate).
Take the cutlets out of the fridge 30 minutes before you want to cook them - so they're not fridge-cold.
Heat the vegetable oil in a large frying pan (skillet) and fry the cutlets for 3-4 minutes on each side until dark golden. You may have to cook in two batches, in which case you can keep the first batch warm in a low oven.
Sprinkle with sesame seeds and shichimi togarashi before serving. I like to serve them with a big green salad.