Thanks to Ali for the inspiration, I was a tad stuck with the mushroom recipe as it needed an ovenproof frypan and mine isn't so decided to look again at the Jamie Oliver gratin.
I took a fair amount of liberty with it and swapped the potato for sweet potato as I had a massive one left over from sweet potato curry last week, I also added a fennel bulb and 2 leeks. For variety I used both red and white onion. I cheated with the breadcrumbs and used shop bought as I never have spare bread.
The result was delicious. I forgot salt and pepper during cooking as I frequently do but with all the herbs (I used a lot, he says handful but it was at least two with sage, thyme, parsley and rosemary from our garden) it wasn't lacking at all.
So thank you Ali, a super result and I'll definately be buying celeriac again!
It was served with a Tesco festive nut roast... I figured it was time we tried one π€£π it was actually very nice. There is half the gratin left over for tomorrow so that's half taken care of too π