Rub the tuna all over with the groundnut oil, then season with salt and lots of black pepper.
Put the sesame seeds on a flat plate. Brush a little more oil over a non-stick pan. Sear the tuna for about 20 seconds on each side.
Take out of the pan and brush very thinly with mustard, then roll quickly in the sesame seeds to coat. Wrap in clingfilm and chill in the fridge for 20 minutes.
Mix the sauce ingredients together. To serve, use a very sharp knife to cut the tuna into ½cm slices. Serve with the sauce.
Rub the tuna all over with the groundnut oil, then season with salt and lots of black pepper.
Put the sesame seeds on a flat plate. Brush a little more oil over a non-stick pan. Sear the tuna for about 20 seconds on each side.
Take out of the pan and brush very thinly with mustard, then roll quickly in the sesame seeds to coat. Wrap in clingfilm and chill in the fridge for 20 minutes.
Mix the sauce ingredients together. To serve, use a very sharp knife to cut the tuna into ½cm slices. Serve with the sauce.