- Put the shiitake mushrooms in a small bowl and add enough warm water to cover.
- Let them soak for about 15 minutes, until soft.
- Put the shiitakes and the button mushrooms in a food processor that has been fitted with the metal blade.
- Process until finely chopped.
- In a large skillet, heat the olive oil ver moderate heat.
- Add the shallot and garlic and saute until tender, 2 to 3 minutes.
- Add the chopped mushrooms and saute, stirring frequently, until all the liquid from the mushrooms has evaporated and they have just begun to brown, 10 to 15 minutes.
- Add the tomatoes, breaking them up with your hands.
- Stir in the tomato paste, sugar, oregano, and basil.
- Simmer until the sauce is thick but still slightly liquid, 10 to 15 minutes.
- Pour over cooked pasta.