Combine white wine, vinegar, salt, pepper, shallots, tarragon, thyme, and cayenne in a pot. Boil until only 2 Tbsp of liquid remain.
Meanwhile, in a separate pan, melt butter.
Place wine mixture in blender. Add 3 egg yolks and beat.
Slowly drizzle melted butter into blender, while it is going, until all is incorporated. Taste for salt & pepper. When ready to serve, top with parsley.