First make the dressing. Mix together the garlic, buttermilk and mayonnaise. When ready to serve, arrange the watercress and iceberg on a plate. Drizzle over most of the dressing, serving any leftovers separately for guests to help themselves
Make it easy
Cut up the iceberg, loosely cover with damp kitchen paper, then leave in the fridge for up to 1 day. Make the dressing and refrigerate for 1-2 days.