Creamy potato and onion gratin

Method

1. Preheat the oven to 190°C/fan170°C/gas 5. Grease a deep, 2-litre baking dish with butter.
2. Peel and thinly slice the potatoes, placing them in a bowl of water to prevent discolouring. Drain then pat dry with a clean tea towel. Arrange with half the onion slices in the dish, overlapping them, and seasoning and drizzling with the melted butter as you go. Finish the top layer neatly with the remaining onion. Top with a bay leaf, then pour over the cream.
3. Cover with foil, place on a baking sheet and bake in the oven below the beef for 45 minutes. Uncover and bake for a further 30 minutes, until tender and golden.