Soak the porcini mushrooms in 1 cup hot water for 15 minutes; drain, and reserve the soaking liquid. Strain the soaking liquid through a coffee filter or paper towel-lined strainer. Reserve 1/2 cup and set aside. (Save the remaining strained liquid for soups or stocks, if desired.) Rinse the mushrooms thoroughly; chop coarsely and set aside.

In a large nonstick skillet, heat the oil over medium heat. Add the porcini mushrooms, button mushrooms, garlic, salt, and pepper. Cook, stirring often, until the mushrooms have started to give off their liquid, 3 to 5 minutes.

Add the marsala and reserved soaking liquid to the skillet; bring to a boil over high heat. Cook, stirring constantly, until the liquids are greatly reduced and syrupy. Remove from the heat and add the parsley, stirring well to combne. Taste and season with additional salt and pepper if needed.

Serve warm with baguette rounds.