In a large pan, heat the oil. Add the onion and fry for 5-6 minutes until golden.
Stir in the chilli flakes, kidney beans, chopped tomatoes, wine and garlic.
Bring to the boil and simmer for 15-20 minutes.
Just before serving, heat a griddle pan until very hot.
Brush the steaks with the olive oil and season with freshly ground black pepper.
Sear the steaks for 2-3 minutes on each side for medium rare and longer if you prefer your meat more cooked.
Remove from the pan and drizzle with the chilli oil and leave the steaks to rest before slicing on the diagonal.
Stir the chocolate in to the chilli con carne.
Meanwhile, while the meat is resting, divide the lettuce between four large plates.
Lay the steak slices on top and spoon the piping hot chilli stew to one side.
Spoon a dollop of sour cream on top. Hand round the chunky guacamole and tortillas.