Begin tossing immediately.
Add the reserved pasta water a little at a time until the sauce becomes glossy and begins clinging to the pasta.
The starch in the pasta water emulsifies the sausage fat, butter, stock and cheese into a silky coating.
No cream is necessary.
7. Finish the dish
Remove the pan from the heat.
Add the Parmigiano Reggiano, Pecorino Romano, the remaining 2 tablespoons of butter, lemon zest and chopped fennel fronds.
Toss until the cheese has melted and the sauce coats every piece of pasta. Add another splash of pasta water if the sauce becomes too tight.
Taste before adding salt. The sausage, stock and Pecorino may already provide all the seasoning the dish needs.
Finish with plenty of freshly ground black pepper.
Serve with another shower of Parmigiano Reggiano, a drizzle of excellent olive oil and chopped parsley, if desired.
A crisp Vermentino or Pinot Grigio would be very much at home alongside it.
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Cook’s Notes
Why blanch the fennel?
Large fennel bulbs can be surprisingly fibrous. Sautéing makes them sweeter, but it doesn’t always make them tender—at least not before the rest of the dish is overcooked.
A brief blanch changes that. Three or four minutes in boiling salted water relaxes the fibers while preserving the fennel’s sweetness and delicate anise aroma. It’s a simple restaurant technique that rarely appears in home recipes, but here it transforms the fennel from a stubborn supporting ingredient into the quiet star of the dish.
Keep the fennel water
Once the fennel is tender, lift it from the pot with a slotted spoon or spider, but don’t pour the water down the drain. Bring it back to a boil and use it to cook the orecchiette.