Prep shrimp: Peel shrimp, cut into ½–¾" oblique pieces. You should have ~275g. Toss with 3g salt and chill.
Aromatics: In a heavy pot over medium, heat olive oil. Add shallot, garlic, and a pinch of salt. Sweat 5–6 min, stirring, until soft and translucent with no browning. Add Calabrian chiles and cook 2 min until oil is fragrant and orange.
Wine: Add 250g white wine, simmer, and reduce until almost dry (au sec), ~2 min.
Cook pasta in sauce: Add 500g clam juice, bring to a lively simmer. Add 225g angel hair pasta directly to the liquid, stirring to submerge. Cook ~2 min, stirring, until just shy of al dente.
Add shrimp: Stir in salted shrimp. Add splashes of clam juice (or water/stock) as needed to keep saucy. Cook until shrimp turn mostly pink and pasta is tender.
Finish: Add cold butter cubes, parsley, and lemon zest. Stir vigorously until butter emulsifies into a creamy, satiny sauce. Adjust with more clam juice if tight.
Serve: Twirl into bowls, top with shrimp, more parsley, and parmesan.
