Knife-and-Fork Egg Salad Sandwiches with Chives
1/2 cup finely chopped chives
2 tbsp. finely chopped celery leaves
Salt and freshly ground black pepper
1/3 cup mayonnaise
2 tsp. white wine vinegar
2 tsp. dijon mustard
4 large slices pumpernickel bread
1 1/2 tbsp. butter, softened
1 small bunch watercress, stems trimmed
1. Arrange eggs in a single layer in a medium pot and cover with cold water by 1". Bring to a boil over medium-high heat, then immediately remove pot from heat. Cover and let rest for 8–10 minutes undisturbed. Drain eggs, leaving them in the pot; shake the pot to crack their shells. Cover eggs with cold water, swish around, then drain. Cover again, this time with icy-cold water (add a few ice cubes if necessary), and set aside to let chill for 20 minutes. Peel and coarsely chop eggs.
2. Combine eggs, half the chives, celery leaves, and salt and pepper to taste in a medium bowl and fold together gently to combine. Add mayonnaise, vinegar, and mustard and fold again, being careful not to mash up the eggs.
3. Toast bread lightly, then butter each slice on one side. Arrange a bit of the watercress on top of each piece of toast, buttered side up. Dollop each piece with a generous scoop of egg salad. Transfer the sandwiches to plates. Sprinkle with remaining chives and serve immediately.