Winter Vegetable Gratin — a plant-based British recipe by BOSH!
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Winter Vegetable Gratin

This is the kind of dish we pull out when we want to genuinely impress people without saying a word. Just let them take a bite and watch their faces. Layers of thinly sliced potato, beetroot, celeriac and sweet potato, all baked in a garlicky, herby plant-based béchamel until golden and bubbling on top. The flavours are rich and earthy, the texture is somewhere between silky and crispy, and honestly it tastes like a proper Sunday dinner centrepiece. Yes, it takes a bit of time and effort, but trust us on this one; every single minute is worth it.

Cook: 75 min
Serves 6

Before You Start

  • Preheat oven to 200°C fan
  • Large baking dish greased with plant-based butter
  • Mandoline or very sharp knife for thin vegetable slicing
  • Small saucepan

Ingredients

  • 2 Maris Piper potatoes
  • 3 large beetroot
  • 1 small celeriac
  • 4 sweet potatoes
  • 2 large escallion shallots
  • 4 cloves of garlic
  • 250ml plant-based cream
  • 100ml plant-based milk
  • 4 sprigs of fresh thyme
  • 4 sprigs of fresh rosemary
  • salt and pepper to taste
  • plant-based butter
  • plant-based cheese

Method

1

Prepare the vegetables

  • Peel and slice the potatoes, beetroot, celeriac and sweet potato into very thin rounds. Set to one side
2

For the bechamel

  • Peel and slice the shallots and mince the garlic
  • Pour the plant-based cream and milk into a small saucepan then add the prepared shallots and garlic. Pick the leaves from the thyme and rosemary and add them to the saucepan with a big pinch of salt and pepper. Bring the mixture to a gentle simmer and leave to cook for 10 minutes
3

For the gratin

  • Grease the baking dish with plant-based butter
  • Grab a stack of the potatoes and line them up in the dish, standing up on a bias. Follow with a row of the beetroot, then celeriac, then sweet potato. Repeat with the remaining veg, creating 8 rows of vegetables. Pour the bechamel mixture over the vegetables. Cover the dish with foil and bake in a hot oven for 30 minutes until the vegetables are tender. Uncover the gratin and sprinkle with the plant-based cheese. Increase the temperature to 200*C fan setting. Return the gratin into the oven, uncovered, and bake for another 15 minutes, until the cheese has melted and the top is golden
4

Serve and enjoy

  • Allow the gratin to sit for 10 minutes before serving with a crunchy green salad

Tips & Variations

  • Get a mandoline if you can: We know it's a bit extra, but thinly slicing all those vegetables by hand is tough going. A mandoline makes it so much faster and gets you those really even, thin rounds that cook perfectly. Just mind your fingers.
  • Layer with intention: Try to alternate your vegetables as you layer them. Add a bit of potato, then a bit of beetroot, then a bit of celeriac. It looks stunning when you cut into it and means every forkful has a mix of flavours.
  • Let it rest before serving: We know it's hard to wait, but giving the gratin 10 minutes to sit after it comes out of the oven means it holds together so much better when you slice it. Well worth the patience.

Why This Works

The trick is getting those vegetables sliced really thin so they cook through properly and absorb all that creamy béchamel. What really makes this sing is infusing the cream and milk with shallots, garlic, thyme and rosemary before it even goes near the gratin. That's where all the depth of flavour comes from, and it makes the whole thing taste like you've been cooking all day, even if you haven't.