Celeriac and Tahini Gratin
This variation on dauphinoise potatoes includes gently mustardy celeriac and tahini, a sticky paste made from sesame seeds that's most often used in hummus. I found that cooking celeriac in a gratin was a great way to introduce my children to the vegetable, though l also love it fresh in a remoulade.
- butter, for greasing
- 800g floury potatoes, peeled
- 1 large celeriac, peeled
- 2 white onions, thinly sliced
- 4 sprigs of thyme, leaves picked
- 200g tahini
- 600ml good-quality vegetable stock, warmed
- ½ tsp fine sea salt
- ½ tsp ground white pepper
- 1 tsp garlic powder
- handful of grated mature Cheddar cheese, to cover the top
- freshly ground black pepper
Preheat the oven to 180°C/160°C fan/gas 4 and grease a large casserole dish (about 26cm) with butter.
Using a mandoline or food processor with a slicer function, if you have one, thinly slice the potatoes and celeriac to a thickness of 1-2mm. The celeriac is tricky to handle due to its size and shape, so cut into half or quarters first for easy slicing.
Arrange a layer of sliced celeriac in the bottom of the greased baking dish and season with a little of the salt and pepper. Follow with a thin layer of sliced onion and picked thyme leaves, then a single layer of potatoes. Season again. Repeat the layering of vegetables and thyme until they have all been used, ensuring 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 through the seasonings of salt, pepper and garlic powder.
Pour the tahini mixture over the layered vegetables, allow it to sink in between the layers, then cover with foil. Bake the gratin in the oven for 1¼-1½ hours.
To test if the gratin is cooked, insert 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 a further 15 minutes until soft (before adding the cheese). When the gratin is cooked, remove the toil, sprinkle evenly with grated cheese and return to the oven for 15 minutes to allow the top to colour before serving. It will be hot so can wait a few minutes.
Find more recipes like this in Marcus' Kitchen, by Marcus Wareing.