Heat oven to 200C/180C fan/gas 6.
Heat the oil in a pan and fry the bacon
for 5 mins until just starting to crisp.
Add the onion and sizzle for 12 mins
until soft and golden.
Meanwhile, tip the potatoes into a large
pan of water, making sure they are well
covered. Bring to a gentle boil, then add
the cauliflower and cook everything for
6-7 mins until both are tender. Tip into
a colander and drain thoroughly.
In a gratin dish, layer the potato and
cauliflower, then scatter with bacon,
onion and a small handful of cheese.
Drizzle each layer with a little cream and
season. Continue until all the layers are
finished, pour over the remaining cream
and scatter with the last of the cheese.
Bake for 30 mins until bubbling. Remove
from the oven and set aside for 1 min to
rest. Serve straight from the dish with
a crisp green salad.