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Crush the peppercorns or just use a grinder. Add to a small saucepan with the vinegar and make a reduction that means boil up to evaporate to almost nothing. Remove from heat.Add a tablespoon of cold water and allow to cool. Melt the butter to a liquid.
In a heatproof bowl i.e a stainless steel or pyrex place the egg yolks. Fit the bowl over a pan of simmering water, add the reduction and whisk with a fine whisk. The mixture has to thicken to the ribbon stage this means to leave a track in the mixture when pulled through.
Remove from the heat and place bowl on a cloth to steady. Gradually add the melted butter whisking in well. Be careful with the milky whey that has separated from the butter. You may add this but you may not need all of it. You will notice that the sauce thickens the more butter you add.
Taste and add salt and pepper as required.
So remember, don't have the butter too hot and don't add it too quickly as it may curdle the sauce. Should this happen place a splash of boiling water in a clean bowl and gradually whisk the curdled sauce onto it. Great with asparagus, cauliflower, broccoli, salmon, turbot.
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