In a small cast iron pan (or sauce pan, but we like the flavor and the way the butter browns a bit more in cast iron) melt the butter over medium heat. Once melted, stir in the flour. The mixture will be chunky. Stir and let brown for 1-2 minutes, then pour in vegetable broth, miso paste, onion powder and pepper. Whisk vigorously until completely combined. Continue to cook over medium heat, stirring occasionally for 3-4 minutes, until the mixture is bubbling and thickening. Turn the heat to low and simmer a few more minutes, until your desired gravy thickness is achieved. Serve immediately!