Place the peppercorns with vinegar in a small sauce pan and completely reduce.
Add 1 tbspn cold water, allow to cool.
Mix in the yolks with a whisk.
Return to a gentle heat and whisking cook to a sabayon (cooking of the yolks to a thickened consistency, like cream, sufficient to sow the mark of the whisk).
Remove from the heat and cool slightly.
Whisk in gradually the melted warm butter until thoroughly combined.
Correct the seasoning.
Pass through a muslin, tammy cloth or fine chinois.
The sauce should be kept at only a slightly warm temperature until served.
Serve in a slightly warm sauce boat.
Serve wit hot fish and vegetables.