Trim the bottoms off each of the sprouts, cutting a cross into each as you go, or at least a slash. This may not be necessary, but I can’t not do it. Then tip them into a large pan of salted boiling water and cook until tender but still retaining a bit of bite, about 5 minutes or so depending on size. Just spoon one out of the water and test (without burning your tongue and thus ruining the whole lunch for yourself) to be sure.

Meanwhile, in a pan large enough to take everything later (or just drain the sprouts and use their pan, once you’ve drained them), cook the pancetta cubes in the oil, with the rind for more salty fat rendering, until they’re bronzed and crisp, but not cooked to the point of having dried out.

Add the butter and the chestnuts and, with a wooden spoon or spatula, press on the chestnuts to break them up a little. When they’re warmed through, turn the heat up and throw in the Marsala, letting it bubble away, fusing with the pancetta fat and chestnutty butter to form a glorious savory syrup. Add the drained sprouts and turn well, sprinkling in half the parsley as you do so. Give a good grinding of pepper; you shouldn’t need salt, given the pancetta, but obviously taste to see. Decant to a warmed serving plate and sprinkle over the remaining chopped parsley.