(Winter) green sauce

If your apartment gets very hot in the winter, or if you've spent the holiday season eating charcuteries and pata negra, or if for some other reason you are tempted by a non-meat based cold meal for a change,  this is a green sauce you can make in the winter and serve with smoked or poached salmon (photo: poached in fish bouillon and left to cool before serving). You could also use it with left-over cold chicken, or roast beef, or some nice charcuterie I guess...
For the sauce,  thaw and drain a small pack of chopped spinach. Mix together ~1 cup / 2 dl of Greek style (i.e. the thicker kind) yogurt with 1 tablespoon of mustard, 1 crushed garlic clove, and whatever dried and / or frozen herbs you have: dill, tarragon, parsley, oregano, with a heavier emphasis on the dill. Mix in the chopped spinach and let the sauce "take" for a few hours in the fridge before serving.
If it looks like there is too much spinach, just set that aside to throw in an omelet, a salad, or something else.