Ingredients :

• The onions — Classic yellow onions. Not red ones — too strong raw, and they take on a weird purple color once cooked. Four onions for four people seems like a lot, but they will shrink by two-thirds during cooking. That’s normal.
• Balsamic vinegar — No need for a 25-euro vintage. Supermarket balsamic works great here — it’s going to cook down and thicken anyway. It’s what provides the depth and acidity that balances the sweetness of the onions.
• Cream cheese — Saint-Morêt or Philadelphia, it doesn’t matter. The important thing is that it’s at room temperature when you incorporate it. Cold from the fridge, it doesn’t mix well with the cream and the texture stays lumpy.
• Double cream (Crème fraîche) — Thick, not liquid. Liquid cream would make a dip that’s too runny and falls off the vegetables with every dip. Thick crème fraîche stays in place and brings the fat that rounds out the balsamic acidity.