Place the cubed celeriac with the garlic in a saucepan with both the olive oil, butter and seasoning. Allow to sauté with the lid on for 35 minutes until soft. Once cooked through add in the crème fraiche and then blitz until smooth and creamy.
For the cavolo nero sauce first remove the stalks, roughly chop then sauté in a pan for around 3-4 minutes before blitzing until completely smooth. Taste and adjust seasoning accordingly.
In a frying pan, add the knob of butter and heat until piping hot and bubbling. Add in the seasoning followed by the chanterelles and cook until golden and crisp.
Serve on a large platter adding the celeriac mash followed by the cavolo nero sauce with a scattering of the chanterelles. Serve with a crusty loaf.