Preheat oven to 425 degrees F.

Lightly season the chicken on both sides with salt and freshly ground black pepper. Coat a medium cast-iron skillet with the oil and set over medium-high heat. Once hot, add the chicken skin-side down, and panfry until the skin is golden and crisp, 8 to 10 minutes. Flip over and transfer the skillet to the oven. Roast until the internal temperature of the chicken reaches 165 degrees F, about 25 to 30 minutes. Transfer the chicken to a plate to cool. (Reserve the golden chicken drippings in the skillet for toasting the bread).

Meanwhile, prepare the mayonnaise. In a small bowl, stir together the vinegar and lemon juice. In a stand mixer, fitted with the whisk attachment, combine the egg yolk, salt, sugar, mustard and 1 tablespoon of the vinegar-lemon mixture. Whisk for a few seconds until the mixture is light and frothy.

With the mixer on a medium speed, add the oil, in a slow steady stream, until you have added half of the oil. This is a very slow process, but you can't rush it. If you do, the mayo will break and the oil will end up pooling. Add the remaining 1 tablespoon vinegar-lemon mixture. Incorporate the rest of the oil in a slow, steady stream. Once all the oil has been added, whisk for another minute, or until the mayo is thick and pale in color. Cover with plastic, or transfer to a airtight container and store in the fridge for up to one week.

Once the chicken is cool enough to handle, remove the skin and bones and discard. Then shred the chicken with your fingers and add it to a bowl. Stir in 1/2 cup chilled mayo, lemon juice, parsley and tarragon. Season with salt and pepper and cover with plastic wrap. Chill until ready to eat.

Heat the cast iron skillet (where you cooked the chicken) over medium heat. Once hot, add the bread slices in a single layer. Toast on both sides until golden brown, about 1 to 2 minutes. Serve the chicken salad, with the mustard, and cornichons. Enjoy!