Thinly slice the onion and soak it in water. Slice the ham as thinly as possible, then thinly slice the asparagus diagonally.
Tightly squeeze any remaining water out of the soaked onion and put it in a heat-resistant container. Then add the asparagus, shiro-dashi, apple cider vinegar and sugar and heat for roughly 1 minute in the microwave. Mix well.
Put the sliced ham and soy sauce into the container as well and once mixed in, wrap tightly and leave to chill in the refrigerator.
Transfer the mixture into serving dishes and serve with a wedge of lemon. Squeeze on the lemon just before eating.
Story Behind this Recipe
The idea for this recipe came from a smoked salmon marinade recipe. Since this ham is also smoked, I thought that you could probably eat it in the same way.
You can use other vegetables instead of asparagus.