Preheat the oven to 375°F with a rack in the center position. Line a rimmed sheet pan with parchment paper. In a food processor, combine the pistachios, generous pinch of salt, mustard powder, thyme, garlic, and pepper. Pulse until finely chopped. Pour the pistachio mixture onto the prepared sheet pan. Place the tenderloin on top and roll until coated on all sides. Roast for 30-35 minutes, or until the internal temperature reaches 145°F on an instant-read thermometer.

Meanwhile, make the sauce by melting the butter in a medium skillet over medium heat. Once the butter is bubbling, add the shallot and cook until softened and translucent, about 3 minutes. Add the garlic and cook until fragrant, 1 minute more. Pour in the white wine and scrape any browned bits from the bottom of the pan. Bring to a simmer and cook until reduced slightly, about 3 minutes. Stir in the chicken stock, salt, pepper, dijon, whole-grain mustard, thyme, sage and rosemary, if using. Simmer until reduced by half, 5-7 minutes. Stir in the heavy cream and simmer until the sauce has thickened slightly, about 5 more minutes. Slice the pork against the grain and transfer to a serving platter. Drizzle with the white wine dijon sauce to serve and enjoy!