Cook eggs in boiling water for 10 minutes. Remove from water, and cool under running water. Peel shells.
Chop eggs coarsely with a knife. Put eggs in a medium bowl, add mayo, and mash with a fork. Add salt and pepper to taste.
Spread butter thinly on Shoku Pan.
Take half of the egg salad and put on a slice of Shoku Pan. Cover with another slice and push gently. Cut off the crusts, and then cut diagonally to make 2 triangles.