Buttery Fluffy Potato Salad Sandwich

Wash the potato thoroughly, then wrap it whole with the skin on in plastic wrap and microwave to save time.

Slice the cucumber lengthwise into thin slices, without cutting into rounds or salting it. Cut to a size that fits the sandwich.

Slice the onion very thinly. Add it to taste, as it gives a textural accent.

Unwrap the heated potato and mash it well with a fork while still unpeeled, then peel the skin off in one go. It is hot, so use chopsticks or similar tools and take care.

Mash the peeled potato with a fork to your preferred texture. Mashing it coarsely keeps a fluffy texture.

Season the mashed potato with a little salt, the thinly sliced onion, olive oil, and vinegar. Finish it as a light, refreshing potato salad without mayonnaise.

Spread mayonnaise and whole grain mustard evenly over each of the two thick-cut bread slices.

Arrange the cucumber on the bread, top with the potato salad, and spread it over the whole surface without pressing down. Layer on the ham and then the cheese, and top with the other slice of bread.

Melt butter in a frying pan, add the sandwich, and brown one side until golden.

Once it smells fragrant, flip it with a spatula, add more butter, and brown the other side until golden. Move it around to coat it all over with butter.

Once both sides are golden brown, remove it and cut into 3 pieces without pressing down, so as not to crush the fluffiness.