The same savory sauce with nothing but veggies.
Combine the miso and water in a small bowl. Stir that stuff until the miso dissolves.
In a 2 quart saucepan, melt the margarine over medium heat. Add the flour and stir until it dissolves, then add veggie broth, miso mixture, soy sauce and onion powder. Cook and stir the mixture over medium heat until it's nice and thick.