Wash, peel, and rewash potatoes. Cut off edges of potato to form a rectangle. Keep edges for cooking with the chicken stock. Slice potato length-wise in 1/4-inch slices. Do the same width-wise, forming 1/4-inch cubes when finished.
Wash, peel, and rewash cucumbers. Cut cucumbers in half; scrape the seeds out with a spoon and cut in half one more time. Then cut into diced cubes the same size as potatoes. You should have equal amounts of potatoes to cucumbers.
Reduce the chicken stock with the potato edges by 75 percent or until the potato edges until they are soft. Smash the potato edges to form a smooth puree.
Blanch the potato cubes in salted water.
Heat extra-virgin olive oil in a saute pan. Lightly sear the shallots and cucumbers. Add the cornichons and vinegar. Cook until everything is al dente, then stir in the chicken stock puree and potato cubes. Season with freshly ground pepper and salt.
For the Parsley Butter: Place the butter in a food processor and blend until smooth. When the butter is smooth, add fresh Italian parsley. Blend the butter and the parsley together until the parsley emulsifies with the butter. Add a touch of salt. Cool mixture to preserve the green color and fresh taste of the parsley.
For the Verjus du Perigord: Over medium heat, melt the sugar, and cook until caramelized and golden brown. Add the verjus and reduce the liquid to 1/3 the volume. Add the veal stock and reduce by 1/4. Remove the foam that accumulates on top of the stock. Add creme fraiche and blend with hand blender. Slowly add the extra-virgin olive oil to form an emulsion and hand blend again.
Preheat the oven to 400 degrees F.
Over a low flame melt a little olive oil and butter in a pan. It is important to keep the temperature very low, so the butter remains brown and maintains a nutty flavor.
Lightly sear the scallops until golden brown on both sides. After searing the scallops, remove them from the pan and place on a drying rack.
Bake for 2 to 3 minutes (depending on the size). The scallops should be medium rare. Reheat the potato-cucumber salad and add the butter at the last minute to retain the color and freshness of the parsley. On a hot, oversized plate, place the potato-cucumber salad in the center of the dish. Place the scallops on top. Drizzle the tops of the scallops with warm verjus and serve.
Recipe courtesy of The Willard, Washington DC