1 tbsp Rapeseed Oil 1 knob Butter, plus a little more for greasing the dish 2 Medium Onions (about 600g), halved and finely sliced Salt and freshly ground black pepper 500g Kohlrabi, peeled and cut into 3mm thick rounds 250g Cornish New Potatoes, scrubbed, washed and cut into 3mm rounds 2 tbsp Parsley, chopped 200ml Double Cream 200ml Water (or chicken or vegetable stock) 1 big handful Spinach,
For the topping
60g Fresh Breadcrumbs 25g Butter, melted 45g Cornish Smuggler Cheddar Cheese
1/Preheat the oven to 190C/375F/gas mark 5. Place a medium-sized frying pan over a medium heat. Add the oil and butter, wait until it foams, then add the sliced onion and a pinch of salt, and sauté for 12 minutes, until soft and starting to take on a little colour.
2/Throw in the kohlrabi, potatoes, and season generously with salt and pepper. Cook, tossing the mixture occasionally, for another five minutes.
3/Pour over the cream and stock, simmer gently until the liquid is reduced by half, stir in the spinach and parsley, then place in a lightly buttered gratin dish, about 30cm x 20cm x 7cm in size, levelling it out with a spatula as you go. Place the gratin dish on a baking tray.
4/Blitz together the breadcrumbs, butter and cheese in a blender, and sprinkle over the top of the filling. Bake the gratin in a hot oven for about 35-40 minutes, until all golden and bubbling.