Step 1

To make the dressing, put the vinegar, sugar, soy, mirin and a pinch of salt in a small pan and bring gently to the boil. Add the katsuobushi, if using, and allow to cool completely, then pour through a fine sieve.

Step 2

Toss the lettuce quarters with the rapeseed oil and a little seasoning. Heat a BBQ or griddle pan to hot, then cook the lettuce, cut-side down, for 1-2 minutes on each side, in batches if necessary, until well charred.

Step 3

Put the pieces onto a plate, pour over some of the dressing and scatter with the toasted sesame seeds.