Bring a large pot of generously salted water to a rolling boil. The water should taste like the sea—this is your only chance to season the pasta from the inside out. Drop in the pasta and cook until al dente, about 1 minute less than the packet suggests. The pasta should feel firm at the centre when you bite into it.

While the pasta boils, melt the butter in a large frying pan over medium heat. Watch for the butter to foam gently, then subside—you’ll hear a soft sizzle. Add the sliced garlic and stir. The garlic should become fragrant and translucent, not brown. If it starts to colour, lower the heat. This takes about 2 minutes, and the kitchen will smell warm and nutty.

Zest the lemon directly into the pan, then squeeze in the juice. The zest will crackle and release a bright, citrusy aroma that cuts through the butter. Stir immediately. The sauce will look thin at this stage—that’s fine. Let it bubble gently for 30 seconds, then pour in the double cream. Stir until the cream and butter emulsify into a pale, golden sauce.

Add the Parmesan cheese, salt, and black pepper. Keep stirring until the cheese melts completely. The sauce should thicken slightly and coat the back of a spoon. If it looks too thick, reserve a cup of pasta water before draining.

When the pasta is al dente, use tongs or a pasta fork to lift it directly from the pot into the frying pan. This transfers a little starchy water with the pasta, which helps the sauce cling. If you prefer, drain the pasta in a colander, but reserve at least 200ml of the cooking water first. Toss the pasta vigorously in the sauce for about 1 minute. The sauce will tighten and become glossy as it coats every strand.

If using chicken, fold it in now. Let it warm through for 1 minute. Taste a strand of pasta—adjust salt or lemon juice if needed. The finished dish should look silky, with flecks of green parsley and tiny specks of lemon zest. Serve immediately, with extra Parmesan on the side.