• 1 (4-to 4 1/2-pound) boneless pork loin roast, trimmed
• 2 tablespoons plus 1 teaspoon olive oil, divided
• 6 rosemary sprigs, divided
• 8 large thyme sprigs, divided
• 8 sage sprigs, divided
• 1/2 cup finely chopped shallots (4 to 5)
• 2 tablespoons finely chopped garlic
• 3 tablespoons Dijon mustard
• 1/3 cup dry vermouth
• 2 teaspoons Dijon mustard
• 1 3/4 cups reduced-sodium chicken broth
• 1 1/2 tablespoons unsalted butter
• 1 1/2 tablespoons all-purpose flour
Preheat oven to 350°F with rack in middle.
Pat pork dry and season with 1 3/4 teaspoons salt and 1 1/2 teaspoons pepper. Brown pork on all sides on stove top.
Put a metal rack in pan and arrange half of herbs down middle of rack. Stir together shallots, garlic, mustard, and 1 tablespoon oil and smear over top and sides of roast, then put roast, fat side up, on top of herbs. Roast 1 hour. Toss remaining herbs with remaining teaspoon oil and arrange on top of roast.
Continue roasting until an instant-read thermometer registers 140 to 145°F, 5 to 15 minutes more (temperature will rise 5 to 10 degrees as it rests). Transfer pork to a cutting board and let rest 15 to 25 minutes.
Make sauce while pork rests:
Remove rack from pan and discard herbs from rack. On stove top, over medium heat combine herb mixture, vermouth and mustard and deglaze by boiling, stirring and scraping up brown bits, until reduced by half. Add broth and simmer 3 minutes. Strain through a fine-mesh sieve into a 2-cup measure. If you have more than 1 1/2 cups, boil to reduce; if less, add water.
Melt butter in a heavy medium saucepan over medium heat. Whisk in flour and cook, whisking, until pale golden, about 3 minutes. Whisk in vermouth mixture and simmer until slightly thickened, about 3 minutes.