Bring Marsala to a simmer in a saucepan. Pour over dried porcini in a bowl, cover, and let stand for 1 hour.Advertisement
Meanwhile, heat 2 tablespoons oil in a nonstick skillet over medium heat. Add sausages, and cook, crumbling with a spoon, until browned, about 8 minutes. Add onion, and cook until softened, about 5 minutes. Using a slotted spoon, transfer sausage and onion to a bowl.
Add 4 tablespoons butter and fresh mushrooms to skillet, and cook until browned, 8 to 10 minutes. Drain dried porcini, reserving liquid, and squeeze in paper towels to remove any excess liquid; coarsely chop. Add dried porcini to skillet along with herbs, prunes, salt, and pepper. Cook for 3 minutes.
Add mushroom mixture to sausages. Strain reserved Marsala through a sieve lined with cheesecloth or a paper towel. (Mushroom-sausage mixture and Marsala can be refrigerated separately in airtight containers overnight.)
Preheat oven to 350 degrees. Place bread on a rimmed baking sheet. Toss with remaining 2 tablespoons oil, red-pepper flakes, salt, and pepper. Bake until golden brown, about 15 minutes.
Add toasted bread mixture and reserved Marsala to mushroom-sausage mixture, and toss. Reserve 2 to 3 cups for stuffing the pork roast (see recipe, page 110). Transfer remaining stuffing to an 8-inch baking dish. Pour stock over top, and dot with remaining 2 tablespoons butter cut into small pieces. Cover with parchment and then foil, and bake for 20 minutes. Uncover, and bake until top is crisp, about 25 minutes more.
Store fresh mushrooms in a paper bag in the refrigerator. They'll stay drier (and last longer) than they will in plastic. Clean with a damp paper towel, which will remove dirt without leaving them soggy. When working with shiitakes, cut off the stems, which are tough and woody. (They can be saved for use in a stock or discarded).