Oven temperature, 200°C/400°F/gas mark 6.

Preheat oven to 200°C/400°F/gas mark 6.

Spread the chopped swede on a baking tray, drizzle with olive oil, season with salt and black pepper and roast for about 30 minutes, or until golden-edged and tender.

Spread the walnuts on a tray and toast in the oven alongside the swede for 6 minutes, or until golden. Roughly chop and set aside.

Heat a little olive oil in a large pan and add the red onion, cooking for about 10 minutes, or until soft, then add the garlic and cook until it just begins to colour at the edges.

Quickly add the flour and stir for a minute to cook out its rawness, then add the stock little by little, stirring after each ladleful so the sauce does not become lumpy.

Strip the kale leaves from the stalks, slice the stalks really finely and tear any big leaves in half.

Add the kale to the pan with the vinegar, put the lid on and allow the kale to wilt for a couple of minutes.

Drain the butter beans and add them to the pan, using a spoon to mash them a little.

Take the pan off the heat and add the mustard, cheese, walnuts, and roasted swede. Stir to combine, taste and season with salt and pepper, then pour into the Le Creuset heritage rectangular dish (26cm).

To make the topping, grate the celeriac using the coarse side of a box grater (you could also use a food processor to do this). Tip the celeriac into a sieve, sprinkle with salt and allow to sit for a few minutes to draw some moisture out. You can squeeze the celeriac with your hands to speed the process up a bit. Transfer the celeriac into a bowl, grate the nutmeg over. Add the thyme leaves.

Give everything a quick mix with your hands, then scatter over the pie filling. Dot with the butter or ghee and bake for 20 minutes, or until the filling is bubbling and the topping golden.