Celeriac and Tahini Gratin
Preparation time: 15 minutes
Cooking time: 90 minutes
Ingredients
Butter, to grease
800g potatoes
1 large celeriac (approx 700g)
2 onions, thinly sliced
4 thyme sprigs, leaves picked and extra for garnish
200g tahini (sesame paste)
600ml hot vegetable stock
1/2 teaspoon fine sea salt
1/2 teaspoon ground white pepper
1 teaspoon garlic powder
Handful of grated cheddar cheese, to cover
Method
- Heat the oven to 160°C (fan)/gas mark 4 and grease a large casserole dish (about 26cm) with butter.
- Peel and thinly slice the potatoes and celeriac as thin as you can (1-2mm)- if you have a mandolin or a food processor with a slicer function you can use that. Tip - you may find it easier to cut the celeriac in half or quarters first.
- Arrange a layer of sliced celeriac in the bottom of the greased baking dish and season with a little salt and pepper. Follow with a layer of sliced onion and thyme leaves, then a single layer of potatoes. Season again. Repeat the layering of vegetables and thyme until they've all been used, ensuring that the final layer of potato is arranged neatly as this will be visible when you serve the dish.
- Whisk the tahini and vegetable stock together in a jug until evenly combined, then mix in the remaining salt and pepper and the garlic powder. Pour the tahini mixture over the layered vegetables, allowing it to sink in between the layers, then cover with foil.
- Bake the gratin in the oven for 1 hour 15 minutes - 1 hour 30 minutes. To test if it's cooked, push a small knife into the centre. The potato and celeriac should be soft all the way through and the knife should meet no resistance. If necessary cover with foil again and return to the oven for 15 minutes more until soft.
- When the gratin is cooked, remove the foil, sprinkle over the grated cheese and return to the oven for 15 minutes to brown. Sprinkle with extra thyme and wait a few minutes before serving - it will be very hot.