Place the egg yolks, water, lemon juice, salt and white pepper in a blender. Cover and blend on high for about 5 seconds. Heat butter to 175 degrees. This allows the butter to cook the yolks as it is added to them. Turn the blender on and immediately begin to add the butter in a steady stream. Incorporate all of the butter in 20 to 30 seconds. If any lumps are present, strain the sauce through a cheese cloth. Add capers.