Heat oil over medium heat, add mushrooms and season with a pinch of salt. Simmer mushrooms, stirring occasionally, until liquid is almost evaporated, about 15 minutes.
Add flour, continue cooking and stirring for about 3 – 5 minutes, at least until the flour has been absorbed and not white anymore. Add 1 cup of broth, stirring/whisking briskly until incorporated and liquid has thickened, there should be no flour lumps, about 5 minutes.
Slowly pour in the remaining broth and mix thoroughly. Season with black pepper and thyme. Simmer at a gentle boil over medium-low until thickened, about 20 minutes, stirring often. Gravy will thicken upon standing. Taste for flavor, adding more salt and pepper as needed.
Makes about 4 cups.
Store leftovers in the refrigerator for up to 5 – 6 days. To freeze, let the gravy cool and store in an airtight container in the freezer for up to 2 months. Let thaw in the refrigerator and reheat in a saucepan, whisking to recombine.
If you find the gravy isn’t thickening up, mix 1 tablespoon oil with 1 heaping tablespoon flour, mix well until completely blended, add to simmering broth, stirring until dissolved, continue cooking until thickened.
I used mushroom gravy when making this recipe which gave it a rich brown color, if using vegetable broth your gravy may be lighter in color.
Make this gluten free by using gluten free flour.