Patate al Forno con Aceto Balsamico e Timo

• 1.3 kg (3 lb) Roseval, or similar yellow waxy potatoes, peeled
• 675 g (

Preheat the oven to 200°C/400°F/Gas 6.

Slice the potatoes lengthways to a thickness of about 1 cm (½ in). Trim the root ends of the onions taking care not to cut them off completely (you want the eventual slices to be held together by the root ends) and cut off the other ends.