Whisk all the ingredients in a small pot and bring to a boil.
Then lower heat to medium to maintain a low boil and whisk often until thickened. Serve warm.
Notes
Make sure to whisk the ingredients at room temperature (before starting to heat the gravy) so the flour doesn't get lumpy.For thicker miso gravy, add an additional 2 tablespoons of flour.For gluten free, use brown rice flour.Leftovers keep refrigerated in a sealed container for up to 5 days, or freeze air tight for up to 3 months. It will thicken as it cools, so loosen with a splash of broth or water, as needed and reheat on stove top.