
Hard boil the eggs according to this recipe. Peel and chop.
In a medium bowl, whisk together the mayonnaise, mustard, lemon juice, salt, and several grinds of pepper.
Mix in the onions, then fold in the eggs, chives, dill, and capers, if using.
Cover and chill in the refrigerator for 20 minutes. Stir, then season to taste and serve.