Pork Roast
In a small bowl, combine the sage, thyme, salt and pepper.
Rub herb mixture all over the pork. Wrap tightly in plastic wrap and refrigerate overnight.
Preheat oven to 250°F and adjust oven rack to center position.
Place pork on a V-shaped rack in a large roasting pan. Transfer to oven and roast until internal temperature reaches 130°F, about 1 1/2 to 2 hours. Remove from oven and tent with foil for at least 20 minutes and up to 40 minutes.
Increase oven temperature to 500°F.
Return roast to oven and cook until crisp and browned on the exterior, about 10 to 20 minutes. Watch closely to make sure the top of the roast doesn’t burn. Remove from oven, tent with foil, and allow to rest for 20 minutes.
Carve the roast by slicing between the bones.
Sauce
Soak dried mushrooms in 1 cup of warm water until softened, swishing around occasionally to dislodge any sand. Using a slotted spoon, lift the mushrooms out of the soaking liquid. Strain the soaking liquid through a paper coffee filter to remove any sand and reserve the liquid. Slice the porcini mushrooms thinly and set aside.
In a large skillet, heat the olive oil over medium-high heat. Cook the shallots, stirring, until very lightly colored, about 3 to 4 minutes. Add shitake mushrooms and cook, stirring, 3 to 4 minutes longer, until softened. Add the porcini mushrooms, salt and pepper and cook, stirring, for 2 minutes. Remove skillet from the heat.
Combine the brandy with the reserved soaking liquid. Add to the skillet with the mushroom. Bring to a boil over medium-high heat. Cook, stirring, for 4 to 5 minutes, until liquid is reduced to1/4 of its original volume. Add the cream and reduce to a light sauce consistency, about 3 to 4 minutes. Stir in the mustard and reseason with salt and pepper if necessary. Serve with the carved rack of pork.