Sauce – How to make a sauce based on tea

If your sauce is too thin, the problem is that your initial roux was either too thin (not enough flour) or you added too much liquid for the amount of roux that you made. Standard ratios are 1 Tbsp butter - 1 Tbsp flour - 1 cup liquid for a thin sauce, 2-2-1 for something in the middle and 3-3-1 for a thick sauce.

Once you've made the sauce and it's too thin, the best fix is to add a beurre manié, which is essentially butter and flour that you mash together in a small bowl and then whisk into your sauce. It's kind of like adding more roux after the fact. However, because it's not pre-cooked like the roux, you need to make sure you give it enough cooking time after adding to get rid of the floury taste.

The usual way is to use a thickener. Some of them require warming, but others do not. Guar or xanthan gum will work if used in the cold sauce. It is the easiest way. If you don't have them, yuo can use gelatine, but you'll have to dissolve it in warm liquid first and then add to the cold sauce, then wait to thicken. None of these will change the taste.

If you are from the "no additives" fraction, you can just use a thicker dairy product. I don't think the heavy whipping cream would be a particularly good fit to yogurt. The best choice would be a fermented product thicker than yogurt, e.g. sour cream or creme fraiche. But you can also use a cheese, although this will change the taste (without making it bad or too different from the original). Good choices would be cream cheese, ricotta, quark, tvorog or mascarpone.