Score the skin of each duck breast with the tip of a very sharp boning knife in a crosshatch pattern, about 1/4-inch deep. Lay each breast on a large entree plate sprinkled with 1 tablespoon of the kosher salt. Set another plate on top of the duck and weigh down with a heavy can. Place in the refrigerator and keep overnight.

Place a 10-inch saute pan over medium heat. Add the butter to the pan and once melted, about 1 minute, add the shallots and cook until translucent and lightly caramelized, about 1 minute. Stir in the garlic and cook for 30 seconds, stirring constantly. Add the mushrooms to the pan and cook, stirring often for 10 minutes. Deglaze the pan with the port wine and cook until it is nearly evaporated, about 1 minute. Continue to cook the mushroom mixture for an additional 3 to 4 minutes.

Remove the duxelles from the heat and allow to cool completely before folding in the Parmesan, pistachios and 1/4 teaspoon of salt and 1/4 teaspoon of pepper. Refrigerate overnight.

The next day, remove the duck from the refrigerator and rinse under cool water. Pat each breast dry with paper towels, and place skin side down, between 2, 12 by 14-inch sheets of plastic wrap. Use a meat mallet, or small, heavy, cast iron pans to pound the duck breasts to about 1/4-inch thickness, measuring about 12 by 8 inches.

Season each breast with 1/2 teaspoon of salt, and 1/4 teaspoon fresh ground black pepper, on the flesh side. Spread 1/2 the duxelle mixture between the 2 breasts, and roll the breasts into a log that will be about 10 inches long. Use kitchen twine to tie the duck at least 4 times with a 1 1/2-inch space between the knots. Repeat this procedure with the second duck breast. Season the rolls on the outside with the remaining salt and pepper.

Preheat the oven to 400 degrees F.

Set a large 12-inch, oven-proof skillet over medium heat, and sear the duck for 3 minutes on the first side, and 2 minutes on the remaining sides. Place the pan in the oven and cook until an instant-read thermometer inserted into the duck roulade registers 140 degrees F, about 5 minutes.

Serve sliced and shingled with the sauce underneath.

Combine the shallots and vinegar in a large saucepan and bring to a boil. Cook until the liquid is reduced by half. Add the chicken stock and reduce again by half. Add the cream and cook, over medium-low heat, reducing the liquid until it reaches a sauce consistency, about 15 to 20 minutes. Remove the sauce from the heat and whisk in the mustard, salt and pepper.

Yield: about 1 1/4 cups