Swedish mustard and dill sauce (Hovmästarsås)

1. In a medium bowl, whisk the mustard, sugar, vinegar, salt and white pepper until smooth.

2. Add the oil drop by drop at first, then in a thin stream, whisking all the time.

3. Keep going until all the oil is used and the sauce is thick, glossy and mayonnaise-like.

4. Wash the dill, pat it dry, remove the thicker stalks and chop it very finely.

5. Stir the dill into the sauce, taste and round it off with a little more sugar or vinegar if needed.

6. Chill for 30 minutes before serving and serve with gravlax or pickled herring.

Tip: Hovmästarsås, "head waiter's sauce", is gravlax's inseparable partner: the sweet and sharp mustard balances the rich cured salmon beautifully. If it splits, start whisking a spoonful of mustard in a clean bowl and slowly drip in the split sauce - it will come back together. If you don't have Swedish sweet mustard, mix Dijon mustard with a little honey.