Crumble the stock cube into a heatproof jug. Pour in 300ml boiling water and stir to mix. Set aside.
Slice the roots off the celeriac at an angle, so you leave as much celeriac behind as possible. Peel off the skin and chop the celeriac into small chunks. Pop in a pan and cover with boiling water. Cover with a lid and bring to the boil. Simmer for 20 mins till the celeriac is soft.
While the celeriac simmers, roughly chop the dried apricots. Pick the thyme leaves off their sprigs (if you have a fine mesh sieve, push the sprigs through the sieves – the leaves will collect in it and you can discard the woody stalks). Peel and thinly slice the onion.
Rub each pork steak with 1 tsp oil and season with salt and pepper. Warm a large frying pan over a high heat. When it’s smoking hot, add the pork steaks. Fry for 2 mins on each side, then lift the steaks out and pop on a plate.
Add the onion to the frying pan. Stir and fry over a high heat for 2 mins to brown it. Pour over the chicken stock. Add the thyme and apricots. Lower in the pork steaks. Place a lid on the pan (or use a baking tray if you don’t have a lid). Simmer on a gentle heat for 15 mins till the pork is cooked though.
When the celeriac is soft when pressed with a fork, drain it then tip back into the pan. Set over a low heat. Cook for 2-3 mins to evaporate off any excess moisture. Add in 2 tbsp crème fraîche and 1 tbsp mustard. Season. Mash together till smoothish. Cover to keep warm.
Finely shred the cavolo nero and place it on top of the pork in the pan. Pop the lid back on and cook for 3 mins till the cavolo nero is tender. Lift the cavolo nero from the top of the pork and place on a couple of plates. Serve with the celeriac mash and pork chops, with the apricot and thyme sauce spooned over the top.