Tomato Sauce with Mushrooms and “Fat Spaghetti”

Place dried mushrooms in a small pot with the stock. Bring to a simmer and reduce heat to reconstitute the dried mushrooms.
 
Bring a large pot of water to a boil for the pasta and preheat a Dutch oven or large sauce pot over medium-high heat with 4 turns of the pan of olive oil. Add pancetta and stir to render, 2 minutes. Add fresh mushrooms and brown. Once browned, season with salt and pepper. Add garlic, onions and sage, and stir a few minutes to soften. Add wine and stir until mostly evaporated.  Add the tomatoes to the mushrooms and stir. Remove porcini mushrooms from their stock and chop; add to sauce. Add all but the last few spoonfuls of stock. Any grit from dried mushrooms will have settled here.