Preheat the oven to 200C/180C Fan/Gas 6.

Arrange the carrots and celeriac to a large roasting tin and the beetroot in a smaller one. Drizzle with ½ tablespoon of the oil each and season with salt and pepper. Roast for 20 minutes. (The beetroot is roasted separately to prevent the colour running, but you can roast them together in one large tin if you prefer.)

Mix the onions with the remaining oil and season with salt. Add to the carrots and celeriac along with the thyme and roast for a further 20 minutes.

While the vegetables are roasting, make the sage and onion balls. Heat the oil and butter in a frying pan, add the onion and fry until softened. Add the sage and lemon zest and remove from the heat. Transfer to a bowl and add the breadcrumbs. Season with plenty of salt and pepper, then stir in the egg until evenly mixed. Shape into eight balls.

To make the sauce, whisk everything together.

Remove the roasting tins from the oven and add the beetroot to the carrots and celeriac. Sprinkle the cannellini beans evenly over the veg. Pour over the sauce. Arrange the balls over the vegetables, then roast for a further 15–20 minutes until the balls are cooked through and browned and the sauce has reduced and formed a sticky glaze on the top of the vegetables.