This recipe is from the Food Network.
10 hard-boiled eggs
¼ cup spicy brown mustard
3 tablespoons mayonnaise
1 teaspoon white-wine vinegar
¼ teaspoon hot sauce
3 tablespoons minced fresh parsley leaves
1 tablespoon drained bottled capers
2 to 3 tablespoons water
Halve the eggs lengthwise, force the yolks through a fine sieve into a bowl, and stir in the mustard, mayonnaise, vinegar, hot sauce, parsley and capers. Stir in enough of the water to reach the desired consistency, add salt and pepper to taste and mound the filling in the egg whites.