Pancetta, an Italian-style bacon, adds rich flavour to this side. Find it at the supermarket deli counter.
Don’t cook pancetta. Boil beans, then drain and plunge into a bowl of ice water to stop cooking. Drain and pat dry with paper towels. Seal in a bag and refrigerate. Slice onions, but don’t cook. Wrap and refrigerate for up to a day. To serve, cook pancetta and continue on with recipe (beans may need a few extra minutes to heat through).