This is a super easy recipe for a cold bearnaisesauce that no one can fail with. :)
250 grams of butter
1 tablespoons red wine vinegar
salt and white pepper, for taste
4 egg yolks
2 tablespoons sour cream
2 tablespoons chopped fresh tarragon and parsley (or to taste)
Melt the butter over medium heat, strain it (remove the white that settles at the bottom).
Add vinegar, egg yolks, sour cream in a high bowl and mix everything with a blender. Pour the melted butter slowly down while the blender is running in the background.
Season with salt, white pepper and tarragon / parsley. Place in the fridge for a thicker texture. :)