Preheat the oven to 400 degrees. Season each filet with Essence. Lightly rub each fillet with the Dijon mustard. Using a cloth napkin, folded in half, cover the bottom half of the napkin with a fourth of the shaved onion. Place the fillet directly on top of the shaved onions. Roll the fish up tightly to the end. This will secure the crust around the fish. In a saute pan, heat the bacon fat. When the fat is hot, saute the fish for 3 minutes on one side, or until the onions are seared and crispy. Flip the fish over and finish cooking in the oven. Roast the fish for 8 to 10 minutes or until the fish is done. In a sauce pot, combine the chicken stock, chervil, shallots, and garlic. Bring the liquid up to a boil and reduce to a simmer. Simmer the liquid for 25 to 30 minutes. Season with salt and pepper. Remove from the heat. Remove the fish from the oven. Mound the potatoes in the center of the plate. Place the crusted fish directly on top. Spoon the sauce around the fish. Garnish with the red pepper paint on the rim and fresh chervil.