Boil the eggs: Place the 8 hen's eggs in a medium saucepan and add enough hot tap water to cover by one inch. Place over medium-high heat and bring to a gentle boil.
The steep: Reduce the heat and simmer for 1 minute, then remove from the heat, cover, and let stand for 9 minutes.
Cooling: Drain the eggs and cover them with ice and cool water to stop the cooking. Let cool completely and peel.
Make the dressing: In a medium mixing bowl, use a whisk to mix the wet ingredients: mayonnaise, mustard, curry powder, dill, and capers. Whisk until the dressing is fully combined.
Whisk-chop the eggs: In a separate large bowl, use a whisk to "chop" the eggs, pressing down to break them apart while ensuring they remain somewhat chunky.
Combine: Pour the prepared dressing over the chopped eggs. Add a fresh squeeze of lemon juice and stir gently to coat.
The fold: Fold in the chopped onion and the celery (using a chunky dice or a finer mince, depending on your preference).
Season: Taste for seasoning, adding more salt or another squeeze of lemon if needed.
Serve: Serve the egg salad on toasted sourdough as a sandwich, as an open-face tartine, or with homemade potato chips. It will keep airtight in the fridge for up to 3 days.