To taste (I use the mustard that comes with a packet of natto mixed with mayonnaise)
Slice the bun in half lengthwise. Slice the cucumber thinly.
Cut the sliced cheese in half too.
Spread the insides of the bun with mustard-mayonnaise. Sandwich in the cucumber, roast pork, cheese, and more cucumber.
Hold together with a pick and it's done.
Story Behind this Recipe
I wanted to increase the number of recipes that children can make on their own.
You can use ham instead of the roast pork, and lettuce instead of the cucumber. Try using grainy mustard and mayonnaise instead of the Japanese mustard too. I used a mandoline to slice the cucumber, but please adjust the thickness to your taste.