Choose a pot big enough to hold all the brussels sprouts in a single layer. (The sweet little black pot in the picture is 6.5" in diameter.) Remove the brussels sprouts from the pot and set them aside.
Cut the pancetta into matchsticks, put them in the pot, and put the pot over a low flame.
While the pancetta cooks, prep the sprouts by peeling off the outer leaves and trimming the ends flush. Don't be lax about this step. The outer leaves will look both waxy and dull, a sort of Crayola Green. Peel them away with your thumbnail and make them into a delicious brussels sprout soup for another meal. For this dish you want each sprout to be a light, bright green. Cut each sprout in half lengthwise.
When the pancetta has cooked through completely and crisped to a rich, dark brown, add the sprout halves and the cream, stir them around, put the top on the pot, and put the pot over the same low flame.
Stir the sprouts and cream from time to time and break up the crispy pancetta.
When the sprouts have cooked through (20-25 minutes), remove the top from the pot and let the cream reduce a little till it is nothing but a sticky, gleaming mass on the sprouts.
Turn the flame off, put the top back on the pot, and let the sprouts cool till they are warm.
Usually the pancetta is plenty salty enough for the whole dish, but check to be sure.
Serve the sprouts alone or with crusty bread as the first course of an otherwise ascetic meal, say a green salad and an apple.