Heat oven to 220C/200C fan/gas 7.
Take the pork out of the fridge and pat
the skin dry. Put the rosemary leaves, salt
and pepper in a mini chopper and grind
together (or do this with a mortar and
pestle). Rub the rosemary salt all over the
pork, making sure it gets into the cuts in
the skin. Sit the pork in a large roasting tin,
ideally on a rack, and roast for 30 mins.
Reduce heat to 170C/150 fan/gas 3 and
roast for 1½ hrs more. Turn oven back
up to 220C/200C fan/gas 7 and roast
for 20-30 mins to crisp. Leave to rest on
a board for 10 mins before carving.
When the pork is nearly ready to come
out, put the celeriac and potato in a large
pan of water, bring to the boil and cook
for 10 mins until just tender. Add the
pears and cook for 2 mins more. Drain
well, then mash until smooth – a mouli
or potato ricer does this job best. Beat
in a splash of cream and some butter,
and serve with the pork and broccoli.