Make the tagliatelle dough from the two flours, eggs and salt following the instructions in this post.

Once it has rested for at least 30 minutes, roll the dough out very thin. Cut the sheet into strips about 7mm (1/4 inch) wide. (See Notes below for details.)

Lay the resulting tagliatelle out on a floured surface until needed.

In a large skillet or saucier, sauté the shallots in abundant olive oil for just a minute or so, until translucent.

Raise the heat and add the crumbled sausage, along with the rosemary and sage. Sauté until the sausage has lost its raw color, breaking up any large chunks.

Now add the mushroom and saute everything over a lively flame until both the mushrooms are well reduced and sausage and mushrooms are lightly brown. Remove the herbs and keep warm until needed.

Boil the pasta in well salted water until al dente, only about 1- 2 minutes.

Drain and transfer the pasta to the skillet, along with a small ladleful of the pasta water. Toss until the sauce coats the pasta nicely.

Then, off heat, add a knob or two of butter and, if using, most of the minced parsley. Give it another toss.

Serve the pasta right away, topped with a final sprinkling of minced parsley if you like.