Heat 2 tbsp olive oil in a pan over medium-low heat and add 2 onions, thinly sliced. Fry, stirring, for 6-8 minutes till softened. Add 4 garlic cloves, finely chopped, and stir for a minute.

Add a bunch of cavolo nero, stalks removed, leaves finely shredded. Stir, cover and cook for 5 minutes, till wilted.

Stir in 2 tbsp Dijon mustard, 2 tbsp fresh thyme leaves, and 600ml single cream. Season with salt and pepper.

Peel and slice very thinly 1.3kg potatoes. Set aside.

Scoop out most of the cavolo nero from the sauce and place in the bottom of a 1.5l baking dish. Arrange the potatoes standing upright over the cavolo nero. Pour over the sauce and sprinkle with 150 manchego cheese, finely grated.

Cover with kitchen foil, and bake for 1 hour 20 minutes at 200c or until the potatoes are tender when pierced with the tip of a knife.

Remove the foil and if not yet golden continue baking without the foil for a few more minutes.