I really love my sauce, enough to whisk in cold butter at the end
It is the technique you've ran into, where you take small blocks/pats of very cold butter and whisk in, off-heat, at the finsih. Makes a sauce rich, velvety and tasty. And fatty. Last two nights running we've had fish, cooked by FIL, so I made Beurre Blanc, which (in my simplified version) is shallots cooked in wine and reduced and mounted with lots of butter. Well, I made it one night and he asked for it again the next night ("Can you make that white sauce again?"). It emulsifies and makes a surprisingly wonderful and quick and easy to prepare sauce for fish and the like. Simple sauces seem like a lost art.
