II
The Method
1
Submerge the baccalà pieces in cold water for 48 hours, refreshing the water every 12 hours. At the end of this period, taste a thin interior flake: it should be savoury but not sharp on the palate. If still aggressively salty, continue soaking and testing at 6-hour intervals.
2
Pat the desalted baccalà dry and dredge each piece lightly in plain flour, shaking off any excess. Heat a wide, heavy pan over medium-high heat with a generous film of olive oil. Brown the baccalà pieces on both sides until a pale golden crust forms — roughly 2 minutes per side. Remove and set aside; the coating should be intact and the flesh not yet cooked through.
3
In the same pan, reduce the heat to medium and add a little fresh oil if necessary. Add the thinly sliced onion and the dried peperoncino. Cook, stirring occasionally, until the onion is fully soft and translucent — 8 to 10 minutes — with no rawness remaining.
4
Add the diced waxy potatoes to the softened onion. Stir to coat in the oil and cook for 5 minutes, until the potato edges begin to turn opaque. Add the crushed San Marzano tomatoes, stir to combine, and bring the contents of the pan to a quiet simmer.
5
This is where the dish lives or dies: nestle the browned baccalà pieces into the tomato and potato base, cover the pan, and reduce the heat to the gentlest possible simmer. The liquid must tremble rather than boil. Braise for 20 minutes until the potatoes yield completely to a knife tip and the baccalà has absorbed the surrounding sauce without breaking apart or turning stringy. High heat at this stage makes the cod rubbery and will cause it to fracture.
6
While the stew finishes, heat a small pan with fresh olive oil until shimmering and very hot. Add the peperoni cruschi and fry for no more than 30 seconds, turning once — they will blister and crisp almost immediately and will blacken if left a moment longer. Lift them out onto paper and, once cool enough to handle, tear into large shards. Reserve the frying oil.
7
Remove the pan from the heat. Scatter the torn cruschi over the surface of the stew and stir them in with a single, gentle fold — they must not submerge into the sauce and lose their crispness. Stir in one tablespoon of the cruschi frying oil and the chopped flat-leaf parsley. Finish with a thread of raw extra-virgin olive oil. Serve directly from the pan.