Step 1

Heat the oven to 200°C/180°C fan/gas Put the celeriac, shallots, mushrooms and most of the thyme sprigs in a large roasting tin, drizzle with 2 tbsp of the oil and sprinkle with salt and pepper. Roast for 25 minutes, turning the vegetables halfway through, until tender and starting to caramelise.

Step 2

Drizzle the remaining 2 tbsp oil into the 1.5 litre baking dish, then warm in the oven for 5 minutes.

Step 3

Meanwhile, for the batter, sift the flour and baking powder into a large mixing bowl, then make a well in the centre. Crack in the eggs, then pour in the milk. Using a balloon whisk, beat to make a smooth batter (you should see bubbles start to appear on the surface). Whisk in the horseradish, thyme leaves and some salt and pepper.

Step 4

Sprinkle the kale into the warm oil in the baking dish/casserole (see tip), then pour in the batter and arrange the roasted veg on top. Bake for 25-30 minutes until puffed up, golden and cooked through.

Step 5

Roughly chop the remaining thyme sprigs, along with the leaves from the rosemary sprigs and the sage leaves. Mix with the salt. Sprinkle over the pud to serve, along with a jug of piping hot gravy, some mustard and horseradish sauce.