Cook the potatoes: Add potatoes to a large Saucier or Stockpot and cover with water. Cover, bring to a boil, then season generously with salt. Remove lid and cook uncovered at a low boil until fork tender, 12–15 minutes.

Drain and pat very dry on a Sheet Pan lined with clean kitchen or paper towels. Allow to cool to room temperature. At this point, potatoes can be used right away or stored in fridge overnight.

Prepare a grill for medium-high heat and preheat a Carbon Steel Half Grill Griddle on the grill for at least 5 minutes.

Cook bacon on solid side of Griddle until crispy and fat has rendered, 3–4 minutes per side. Take care to wipe up any excess bacon grease flowing to perforated side with a kitchen or paper towel to avoid flare ups.

Transfer bacon to a paper towel-lined plate and wipe up all but about a Tbsp. of bacon grease from Griddle.

Place potatoes in a large bowl and toss with a little oil. Working in batches (8–9 at a time), add potatoes to solid side of Griddle and use a Grill Press to smash them about ½” thick. It’s OK if some of them break apart and have irregular edges. Season with salt and pepper.

Cook until golden brown and crispy on bottom, about 3 minutes. Flip potatoes and move them to perforated side of Griddle. Season with salt and pepper. Cook until golden brown and crisped on other side, about 3 minutes more. Transfer back to large bowl. Repeat with remaining potatoes.

Make the dressing and assemble salad: Add vinegar, whole grain and Dijon mustard, smoked paprika, sugar, ½ teaspoon salt and a few grinds of black pepper to a medium bowl. Whisk to combine. Stream in oil while whisking until dressing is emulsified.

Crumble bacon. Add ⅔ of bacon, cornichons, 2 Tbsp. parsley, and scallions to bowl with potatoes. Drizzle dressing over top and fold to coat potatoes with dressing. Taste and adjust seasoning. Top with remaining bacon and parsley. Serve warm or at room temperature.