Place eggs in a medium saucepan, cover by with cold water by 1 inch or from your fingertip to first knuckle. Bring to a boil over high heat. Remove from heat, cover with id and let sit for 10 minutes. Cool with cold water and ice cubes for 5 minutes. Crack and peel eggs under cold running water. Set aside.

In a bowl mash eggs finely. Add mayonnaise, mustard and salt and stir to combine.

Toast bread, butter and top two slices with half of egg mixture. Top with remaining bread slices and serve.