Step 1

In a medium saucepan, combine the potatoes, broth and 1 teaspoon salt. Add enough water to just cover the potatoes. Bring to a boil over medium-high then reduce to medium-low and cook until a skewer inserted into the potatoes meets no resistance, 8 to 10 minutes. Reserve ½ cup of the cooking liquid, then drain the potatoes and transfer to a large bowl. Sprinkle with the cornichon brine, 1 tablespoon of the vinegar and ½ teaspoon pepper.

Step 2

In the empty pan, combine the reserved cooking liquid with the onion and caraway seeds and bring to a simmer over medium-high. Pour the mixture over the potatoes and stir well.Let stand, stirring occasionally, until the liquid has been absorbed, about 10 minutes.

Step 3

In a liquid measuring cup or small bowl, whisk together the oil, mustard, remaining 1 tablespoon of vinegar, 1/4 teaspoon salt and ½ teaspoon pepper until emulsified. Pour the mixture over the potatoes and add the celery, cornichons, dill, and eggs, if using, then fold until well combined. Taste and season with salt and pepper. Serve at room temperature.