Method

• Preheat your oven to 200˚C/180˚C fan-assisted/gas mark 6. In a bowl, whisk the double cream, milk and crème fraîche together. Season with salt and pepper. Set aside.
• Peel the celeriac, sweet potato and swede. Slice about 1cm thick. Butter a gratin dish and arrange the root vegetables, seasoning each layer and adding a good handful of cheese before adding the next layer of vegetables. Pour over the cream mixture and sprinkle with any remaining cheese. Cook the gratin for 45-55 minutes until golden brown.
• Meanwhile, slice the leeks and wash to remove any grit. Heat a little oil in a frying pan and gently cook the leeks for 3-4 minutes until soft. Strip the leaves from the thyme sprigs and add to the leeks, season with salt and pepper. Drain the cannellini beans and add to the leeks. Taste and adjust the seasoning if needed.
• Once the gratin is bubbling away, remove from the oven and scatter over the leek and bean mix. Top with slices of cooked beetroot and scatter over the breadcrumbs. Bake for 25-30 minutes.