Oubaek Bearnaise

From Oubaek in Copenhagen. The chef made Bearnaise sauce cool again, spawning a steakhouse chain whose claim to fame is this very sauce. But we had it at the source and I think I managed to squeeze its secret ingredients from a nice young lad serving us! Apparently the trick is to make a tarragon essence containing various seasonal vegetables that gives the vinegar going into the sauce a bit more complexity and presence.

tarragon essence

250 gr freshly clarified butter, cooled to tepid

4 egg yolks

2 tblsp snipped chervil

juice of 1/2 lemon

maldon sea salt

10 peppercorns, crushed

tarragon essence

2 tblsp white wine vinegar

3 tblsp snipped tarragon

30 gr chopped shallot

2 tblsp of chopped parsnip, carrots, celery

1. to make the essence, combine the wine vinegar, vegetables, snipped tarragon, the shallot and pepperorns in a small, heavy-based saucepan and reduce by half over a low heat; set aside to cool
2. combine essence, egg yolks and 3 tblsp water; set the pan over a low heat and whisk continuously, making sure that the whisk reaches right down into the bottom of the pan
3. as you whisk, gently increase the heat; the sauce should emulsify slowly and gradually, becoming oil after 8-10 minutes (don't let it get hotter than 65 c)
4. turn off the heat and whisk the clarified butter into the sauce a little at a time
5. season with salt and pepper, pass the sauce through another sieve into another pan; stir in the rest of the tarragon, the chervil and lemon juice
6. check for seasoning and serve at once