Melt the butter without it turning brown. Stir the egg yolks and 3 tbsp. water. Place the bowl in a bain-marie and whisk the sauce until it thickens. Beat in the butter. Not too hot, then it curdles. Season with salt, pepper and lemon juice. Remove the pan from the heat but leave the bowl on it. Beat the whipped cream until stiff and lightly fold it into the sauce.