Put the pork into a shallow container, skin side up.
Spread the salt evenly over the skin.
Place in the fridge for at least 6 hours
Preheat the oven to 200°C
Brush the salt off the pork, dry well with paper towels and score the skin in parallels about 2cm apart.
Put the fennel seeds, garlic and oil in the bottom of a roasting dish
Place the pork on top, making the skin side as level as possible by packing the pork with rolled up pieces of tinfoil.
Place in the oven for 1 ½ to 1 ¾ hours or until the skin is well crisped.
Remove from the oven, cover with foil and rest
Put the kumara on a roasting tray and place in the oven for 1 hour or until very tender.
Remove from the oven and cool
Cut in half and scoop out the flesh and put it into a bowl.
Add the honey, mash it up and season
Put the purée into an ovenproof dish just big enough to hold it.
Smooth the top and pour on the cream
Sprinkle the breadcrumbs evenly over the top
Place in the oven for 15-20 minutes until bubbling and well browned.
Drop the silverbeet into boiling water and boil 5 minutes.
Remove from the heat drain well, squeezing out any excess water.
Place in a large warm bowl.
Add the zest, juice, oil and season
Mix well.
Serve the pork, sliced, with the gratin and silverbeet on the side.
