First, prepare the roux by heating the olive oil in a small pot over medium heat. Sprinkle the flour over the olive oil and, whisking constantly, cook for 4-5 minutes until the mixture is golden in color and smells a bit “nutty”. Remove the pot from the heat and set the roux aside until needed.
Chop the shallots and mushrooms. Heat the olive oil in a pot over medium heat. Add the shallots and sauté for 2 minutes. Add the mushrooms and continue to sauté, stirring regularly, for an additional 3 minutes.
Raise the heat to high and add the stock, mushroom soy sauce and white pepper. Bring the mixture to a boil and immediately turn the heat down to low. Add the roux that you prepared earlier and whisk it in completely. You don’t want any “roux lumps”.
Simmer the gravy, whisking regularly, for approximately 7-10 minutes or until it has thickened slightly. Remove the pot from the heat and whisk in the miso until it has completely dissolved.
Remove the pot from the heat and carefully puree the gravy in batches in your blender until it is smooth. Transfer the gravy to a clean pot and keep warm over very low heat until you’re ready to serve.