Mix the ingredients for the wasabi mayonnaise in a small bowl and set aside.
Do the same for the sriracha mayonnaise and set aside.
Making the sandwiches
Cut the crusts off the sandwich bread.
Spread butter on each slice of bread and a little wasabi mayo (or sriracha mayo).
Put two layers of tomatoes on the bread and add two layers of cucumber on top. Season with salt and pepper and finish by topping with another slice of bread.
Notes
These finger sandwiches are eaten on the same day.