Enrich wine based sauces by whisking in a large knob of cold butter at the very end, it will give your sauce a richness, shine and round off any acidic flavours.
Never microwave! These are fragile emulsions and will split. Reheat by gently whisking over a double boiler on low heat. If the emulsion begins to split, try whisking in a spoonful of warm water, never add more butter.