- In medium-sized pan, melt butter. Add onion and anchovy; sweat it until tender without browning it.
- Add diced celery root; sweat it for about a minute in the butter and onion and anchovy. Add ladle-fulls of warm water a little at a time to keep the mixture moist as it cooks, stirring continuously.
- After about five minutes, add in green apples and mustard.
- Warm it through about 1−2 minutes.
- When celery root is al dente, add the whipped cream and fold it in.
- Adjust seasoning with a little bit of lemon juice and salt. Serve warm. It should have the consistency of traditional risotto.