Place peas in pan and heat over medium heat until warmed and liquid evaporates.

Take peas off heat. Chop eggs and add to peas.

Add mayonnaise, mustard, onion, and salt and pepper to pea mixture.

Place salad in bowl with lid to cool. Add thinly sliced boiled egg on top.

Refrigerate for at least one hour to cool. Keep any leftovers in refrigerator.