Dry roast the sesame seeds in a small frying pan until lightly coloured then put into a bowl.
Squeeze 1 teaspoon juice from the lemon and add to the seeds. Finely chop the herbs, reserving a few sprigs for a garnish, then stir the chopped herbs into the sesame seeds along with the butter, wasabi paste, soy sauce and Tabasco. Beat until smooth.
Shape the butter into a sausage, wrap in foil and chill in the freezer.
Heat a ridged griller plate or frying pan over moderately high heat. Brush both sides of the tuna steaks with the oil and fry for 3–4 minutes on each side.
Cut the butter into rounds. Transfer the steaks to four plates, place a round of butter on each and garnish with the herb sprigs.
Radishes, pickled ginger, bean sprouts and watercress all make good garnishes for this dish. Steamed new potatoes are a good foil for the flavoured butter.
NUTRIENTS PER SERVING:
good source of vitamins A, B group and E, and selenium.