Bohemian Sauce

Ingredients

• 1.5 dL béchamel (thick white sauce), very thick and well chilled
• 4 whole egg yolks
• 10 g salt
• pinch pepper
• a few drops vinegar
• 1 L oil
• 2 tbsp tarragon vinegar
• 1 tbsp mustard

Instructions

1. Combine in a bowl: the very thick, well-chilled béchamel (thick white sauce), egg yolks, salt, a pinch of pepper, and a few drops of vinegar.
2. Whisk everything together thoroughly, then add the oil and tarragon vinegar in the same manner as you would prepare ordinary mayonnaise—that is, adding the oil slowly while whisking constantly to form an emulsion.
3. Finish the sauce by whisking in the mustard.