Preheat your oven to 160˚C.
Wash your celeriac. Prick with a knife, around 1cm in to ensure it cooks, and the flavour gets into the celeriac. Place a large piece of foil on to a baking tray and pop your celeriac on and tuck the herbs, garlic cloves and butter around, season and wrap in 3 layers of foil.
Bake for 2 hours, check about 2/3 way through to see if it is cooking through. When you’re ready to serve simply cut into wedges, and keep the garlic to serve on the side. Depending on your celeriac, you can eat the skin if it isn’t too tough.