French onion soup is an ancient dish. About as peasanty as things can get without holding a pitchfork, this humble, thick beef broth with caramelised onions and tres rustique cheese toasts is a classic. It screams of the open skies of France, of blue smocks and Breton cider. We've gone for a dry Marsala for the kick which is, admittedly, from Sicily, but we believe in the power of European cooperation. We've also put it on hasselback potatoes, because you guys seem to be into that.
- Slice the potatoes in parallel cuts 3/4 of the way through. Brush with oil and sprinkle with salt and pepper, then bake at 180°C for roughly an hour to allow the potatoes to cook through and fan out.
- Meanwhile, heat the oil and butter together on a medium in a heavy, wide rimmed pan. Add the onions and cook very gently for around 40 minutes (putting a lid on speeds things up a bit). Near the end of cooking time add the garlic and stir through for a minute, then add the sugar and stir through to caramelise the sugar. Keep cooking for another 5 - 10 minutes until the onions are really sticky.
- Add the flour and stir together to coat the onions. Turn up the heat to cook out the flour, then gradually beat in the stock, a little at a time, to make a thick sauce. Pour in the marsala and reduce a little to a thick, gravy like sauce.
- Spoon this over the potatoes and top them with slices of gruyere and pop them back in the oven - when this melts it'll trickle into the cracks in the potatoes.
- Serve with a crisp salad and lots of the onion sauce.