Ingredients

Step by step

1. Preheat the oven to 220°C, fan 200°C, gas 7. Melt the butter in a large frying pan. Add the onions and a pinch of salt, cover with a lid and cook gently for 5 minutes, then remove the lid and continue to cook over a low heat for 10 minutes, stirring occasionally until softened but without allowing to colour.
2. Meanwhile, cut the potatoes into roughly 2cm chunks. Transfer to a large roasting tin and add the leaves from 1 sprig of thyme, the oil and some seasoning. Toss well and roast for 25-30 minutes until tender, golden and crispy. Put the sausages in a separate roasting tin and cook below the potatoes, for 20-25 minutes until cooked through and nicely browned.
3. Increase the heat under the onions to high, add the remaining thyme leaves and the wine and allow to bubble off completely (3-4 minutes). Reduce the heat to low, sprinkle in the sugar, add the mustard and cook for 15 minutes, stirring occasionally, until they are caramelised.
4. When the potatoes are cooked, add the sliced cornichons and mix well. Split the hot dog rolls (if using a baguette, warm through in a moderate oven for 5 minutes), add a little cheese and a sausage to each, then spoon over some caramelised onions and more grated cheese. Serve warm, with the crispy potatoes on the side and extra mustard.