First get all of the seasonings ready. This isn't meat so you don't have to cook it for long on the stove. Then pulse the mushrooms and walnuts in the food processor and set aside.
In a medium skillet sauté add 1/2 of the chopped onions and garlic for 3 - 4 min. Then add in the mushroom and walnut mixture and stir together. Once that's done, add in all the seasonings, tomato paste, tamari, rest of the onions and water mixing it all together.
Stir everything until heated through. Be sure to taste it. If you need to adjust the seasonings do so before serving. It can be eaten on a bun or lettuce cups. Enjoy!