Melt the butter in a heavy skillet and allow to bubble slightly. Add the crushed garlic, onions, and diced mushrooms. When mushrooms are limp, add 1 cup bouillon and increase heat so that mixture becomes somewhat reduced in volume. Add the wine and season with salt. Reduce heat and simmer.
Mix the flour with the 1/4 cup bouillon. Add this gradually to the mixture in the skillet until it thickens. Be sure to stir so that the sauce is smooth.