Vegetarian Gravy

Begin by cutting a yellow onion in half and cutting off the bottom.
Medium-dice half of the yellow onion.
Remove the stems from the mushrooms and use a paper towel to remove any dirt.
Finely dice the mushroom caps as small as possible.
In a medium non-stick pot, add olive oil and 1 tablespoon of butter over medium heat until melted.
Add the diced onion. Stir gently, then don't touch until the bottoms begin to brown.
Once browning begins, stir once, and then wait again for more browning.
Repeat this process until the onions are completely browned and slightly caramelized.
Add the minced mushrooms and stir to combine. Sauté for about 1-2 minutes.
Add another tablespoon of butter and let that melt.
Then, sprinkle in the flour.
Stir to combine, making sure that the flour incorporates fully. Continue stirring for about 1 minute, so that the flour is cooked.
De-glaze the pan with the soy sauce. Allow it to simmer and slightly evaporate.
Pour in the broth slowly, stirring or whisking to combine.
Once the broth is added, continue whisking until very thick.
Let it simmer and taste to ensure there is no raw flour taste.
Season with salt.
(Optional, but highly recommended) Remove from heat and pour over a fine-mesh strainer over a bowl or cup.
This will take a minute or two, but use a rubber spatula to move the grave around in the strainer, until nearly all of the liquid is through the strainer.
Serve hot and enjoy!