Melt the butter in the bowl for 5 minutes at 70 °C on speed 2. Set aside the melted butter. Prepare the remaining ingredients while the bowl cools.Peel the shallot and blend for 10 seconds on speed 5. Scrape down the sides of the bowl with a spatula. Add white wine, vinegar, tarragon and pepper.Heat for 10 minutes at 100°C on speed 2, removing the stopper. Strain the stock and allow to cool.Rinse the bowl. Place egg yolks in bowl and pour in stock. Mix for 20 seconds on speed 5.Heat for 10 minutes at 70 °C on speed 3 without the lid. After 2 minutes, slowly pour the melted butter through the hole in the lid.Season the sauce with salt, pepper and herbs: tarragon. Stir for 30 seconds on speed 3 and serve.