Lift the fennel from the water with a slotted spoon or spider and allow it to drain thoroughly.
Don’t discard the water. Return it to a boil and use the same pot to cook the orecchiette. The water will carry a faint sweetness and aroma from the fennel into the pasta.
2. Brown the sausage
Heat the olive oil in a large Dutch oven or wide sauté pan over medium-high heat.
Add the sausage and cook, breaking it into irregular bite-sized pieces rather than tiny crumbles.
Let it brown deeply before moving it too much. Those caramelized edges are essential to the flavor of the finished sauce.
Transfer the sausage to a bowl, leaving the rendered fat in the pan.
3. Build the vegetable base
Reduce the heat to medium and add 1 tablespoon of the butter.
Add the blanched fennel and cook for about 5 minutes, until it begins to take on a little color.
Add the mushrooms. Spread them across the pan and resist the urge to stir constantly.
Good mushrooms brown. Constantly stirred mushrooms steam.
Let them develop color before turning them. Once they’ve released most of their moisture and begun to caramelize, add the shallots.
Cook for 3 to 4 minutes, until the shallots have softened.
Add the garlic, thyme, rosemary and crushed red pepper flakes. Cook for about 1 minute, just until fragrant.
Don’t let the garlic brown.
4. Deglaze the pan
Pour in the white wine and scrape up every browned bit from the bottom of the pan.
Simmer until the wine has reduced by roughly half.
Add the chicken stock and return the sausage to the pan.
Simmer gently for about 5 minutes.
5. Cook the pasta
Return the fennel-blanching water to a vigorous boil.