-
1
Soak porcini mushrooms in 2 1/2 cups warm water for 1 hour (using a 4-cup Pyrex measuring cup works well).
-
2
Using a slotted spoon or tongs, transfer mushrooms to drain on paper towels.
-
3
Gently pour most of the soaking liquid through a fine-mesh strainer suspended over a small bowl, being careful not to disturb the particles of sand that have sunk to the bottom.
-
4
Save about 2 cups of the liquid and throw out the rest; finely chop the porcini mushrooms and set aside.
-
5
Add onion, carrots, celery, garlic, parsley, olive oil, salt, and pepper flakes in a large straight-sided saute pan.
-
6
Saute over medium-high heat for about 10 minutes, until vegetables are soft.
-
7
Add in mushrooms (except for the porcini), sage, rosemary, and bay leaf; stir/saute over high heat for 5 minutes.
-
8
Add in porcini and wine; cook/stir until most of the wine has evaporated.
-
9
Add 1 cup reserved mushroom water and pureed tomatoes; bring to a boil; decrease heat, and simmer 20 minutes.
-
10
If sauce seems too dry, add a bit more of the mushroom water.
-
11
Taste and adjust seasoning with salt.
-
12
Bring a large pot of water to a boil; add salt and spaghetti.
-
13
Cook, stirring often, until al dente; drain and transfer to a large serving bowl.
-
14
Spoon some of the sauce over the spaghetti, dot with butter; toss and sprinkle with Parmigiano-Reggiano and toss again.
-
15
Serve immediately, passing more sauce and cheese at the table.
