Steps

1. Trim the ends off 1 cucumber.
   🕒 01:16
2. Cut the cucumber in half.
   🕒 01:25
3. Using a small teaspoon, carefully remove the seeds from the cucumber. (This is the key!) Removing the seeds prevents sogginess.
   🕒 01:41
4. Thinly slice the deseeded cucumber lengthwise on an angle. Slice as thinly as possible. (This is the key!) Thin slicing creates a crispy texture. If this feels tedious, you can use a slicer.
   🕒 02:13
5. Dissolve 1/2 tsp salt in water to make a saltwater solution.
   🕒 02:41
6. Soak the sliced cucumber in the saltwater. (This is the key!) Soaking in saltwater makes the cucumber texture crisp and adds a subtle, delicious saltiness. If you're doing a salt brine, about 1/4 tsp of salt per cucumber is usually good.
   🕒 02:49
7. On one side of 1 slice of shokupan, spread a mixture of 1 tsp Japanese mustard paste and 1 tbsp mayonnaise. (This is the key!) Applying a layer of fat prevents moisture from the filling from soaking into the bread.
   🕒 03:56
8. On one side of the other slice of shokupan, thinly shave and scatter butter (as needed) using a knife. (This is the key!) This saves time by not needing to melt the butter and adds a nice accent to the bread.
   🕒 04:28
9. Place 4 slices of roast ham on the buttered side of the shokupan.
   🕒 05:19
10. Place 2 slices of sliced cheese on top of the roast ham.
    🕒 05:42
11. Drain the cucumber that was soaked in saltwater and thoroughly pat dry with a paper towel to remove excess moisture. (This is the key!) Thoroughly squeezing out the moisture concentrates the cucumber's flavor and prevents the sandwich from becoming soggy.
    🕒 05:46
12. Place about half of the squeezed cucumber on top of the sliced cheese.
    🕒 06:19
13. Place the shokupan with the mustard-mayonnaise spread on top to cover, and gently press.
    🕒 06:36
14. Wrap the sandwich tightly diagonally with plastic wrap and let it sit for a while to allow the shape to set.
    🕒 06:42
15. Remove the plastic wrap and trim off the crusts from all four sides of the sandwich. (This is the key!) Cutting off the crusts makes the sandwich soft and easy to eat.
    🕒 07:00
16. Cut the sandwich into three equal portions along the longer side and plate.
    🕒 07:16