If you haven’t done so, cook quinoa and set aside to cool. To prepare 1 cup cooked quinoa: Add 1/3 heaping cup (65 g) dry quinoa to a small saucepan and toast for 2-3 minutes over medium heat. Then add 2/3 cup (160 ml) water and bring to a boil. Once boiling, cover and reduce heat to a simmer. Cook for 10-15 minutes or until water is absorbed. Then fluff with a fork, remove from the heat, and crack the lid so the quinoa can cool.
Heat a large skillet over medium heat with the sesame oil. Once hot, add the mushrooms and sauté for 10-15 minutes, stirring occasionally, until they are lightly browned and have released most of their moisture.
Drain and rinse the black beans, then dry in a clean kitchen towel.
To the sautéed mushrooms, add the black beans, garlic, green onion, ginger, and tamari (or soy sauce or coconut aminos). Sauté for 3-4 minutes, or until slightly softened, stirring frequently. Set aside to cool slightly.
Preheat the oven to 400 F (200 C) and set out a baking sheet.
Transfer the mixture to a food processor and pulse until no large pieces of beans or mushrooms remain, being careful not to overmix into a paste.
Add 1 cup (185 g) cooked and cooled quinoa (adjust amount if altering batch size) and the maple syrup (or agave or honey). Pulse to combine until a textured dough forms, again being careful not to overmix.
Taste and adjust flavor as needed, adding more tamari for saltiness/depth of flavor, sesame oil for nuttiness, or maple syrup for balance. If it’s too wet, add more quinoa and pulse to combine.
Scoop out 1 ½-Tbsp portions of dough and gently shape into round balls using wet hands. Recipe as written makes ~15 meatballs. Add formed meatballs to a bare or parchment-lined baking sheet.
Bake for 15 minutes. Then flip to ensure even baking and bake for another 10-15 minutes, or until golden brown and slightly dry to the touch.