In any sauce you make, start with a concentration of flavors with great acidity. You then re-dilute the sauce, but the proportion of liquid you add should not be so high that you wash away the extracted flavor you're aiming to create.

It's not good to thicken sauce with too much butter because it can cause heaviness. You don't want to avoid butter, but you also don't want to put too much - add it slowly.

Sauce is certainly ancestral to French cooking. The technique is very tricky, but it's also very fundamental.

Daniel Boulud Quotes