Melt the butter in a pan on medium heat, add the mushrooms and onion.
Saute until the mushrooms are brown and the onions have turned translucent.
Remove from the pan.
Add a splash of stock to deglaze and then add the remaining stock.
Add the oregano, thyme, and bay leaves, bring to a boil. Turn down the heat to medium and let simmer for about 5 minutes.
Add the wine and bring back to a boil. Turn down the heat to medium and let simmer for 5 minutes.
Add 2 teaspoons of arrowroot powder that has been mixed with a bit of cold water. Whisk in and bring back to a boil. Turn down to medium heat and let simmer for 5 minutes.
If the sauce has not thickened, add arrowroot powder (mixed with a bit of cold water), 1 teaspoon at time, bringing back up to a boil each time and then turning down to medium.
Once it begins to thicken, add the mushrooms and onions back in.
Add a few dashes of worcestershire sauce, and taste for addition of salt and pepper.
Let simmer until desired thickness.
Serve over slices of London broil.