Potato and sweet potato dauphinoise

  • Preparation time: 25 minutes
  • Cooking time: 60 minutes
  • Total time: 1 hour 25 minutes 60 minutes 25 minutes

Serves: 6

Ingredients

15g unsalted butter, plus extra for greasing
1 onion, finely sliced
1 garlic clove, crushed
1 tbsp thyme leaves
170ml single cream
170ml double cream
100ml whole milk
500g king edward potatoes, peeled and finely sliced
500g sweet potatoes, peeled and finely sliced

Method

1. Preheat the oven to 170˚C, gas mark 3; grease a 1.5 litre baking dish. Heat the butter in a large saucepan over a medium heat until foaming. Stir in the onion and cook for 5 minutes until softened. Add the garlic and thyme and cook for another 3 minutes. Add the creams and milk to the pan and bring gently to a simmer; season.

2. Tip the king edward potatoes into the pan, simmer for 6–7 minutes, then add the sweet potatoes. Stir, then tip everything into the baking dish. (You can chill the dish overnight at this point; bring it back to room temperature before continuing to cook.) Bake for 1 hour until the top is golden and the potatoes tender, then serve.