For umami sauce, in medium saucepan, heat oil over medium and sauté garlic and ginger for 30 seconds to 1 minute, until fragrant. Whisk in maple syrup and tomato paste and cook for a few seconds. Slowly whisk in broth, vinegar, and tamari, and bring to a simmer. Simmer, uncovered, for 15 to 20 minutes, until thickened slightly. Continue to cook, uncovered, if a thicker sauce is desired. Store sauce in airtight container in the fridge for up to 2 weeks. Enjoy leftover sauce on grain bowls and steamed greens throughout the week.