Begin by placing fresh, room-temperature eggs in a saucepan and covering them with cold water. Bring the water to a rapid boil over medium heat, then cover the pot and turn off the heat. Let the eggs steep in the hot water for 9-12 minutes.

Once the eggs have finished cooking, carefully transfer them to a bowl filled with ice-cold water and allow the eggs to sit for about 5 minutes.

While the eggs are cooling, take your soft white bread and trim off the crusts using a sharp knife.

Once the eggs are completely cooled, gently tap them to crack the shells and peel them. Mash the peeled eggs in a mixing bowl until slightly coarse.

Add Kewpie mayonnaise, a pinch of salt, and pepper to the mashed eggs. Stir until creamy but avoid overmixing.

Spread softened butter on one side of each trimmed bread slice.

On two of the buttered slices, generously spoon the egg filling, spreading it out evenly. Top with the other slices, buttered side down.

Slice the assembled sandwiches into triangles or rectangles as preferred and serve immediately or wrap for later.