Begin by finely chopping the onion, carrot, garlic, celery, and optional mushrooms. In a large pot, heat 1 tablespoon of water over medium heat and sauté the chopped vegetables for 6-7 minutes.

Add sea salt, black pepper, paprika, dried thyme, onion powder, and cumin to the sautéed veggies in the pot. Continue sautéing for an additional 2 minutes.

In a food processor, combine rolled oats, nuts (if using), and flaxseed, pulsing until you achieve a grainy flour consistency. Then, add the drained chickpeas, soy sauce, and tomato sauce. Pulse until combined but still slightly chunky.

Transfer the mixture to a large mixing bowl and pour in the sautéed vegetable blend. Mix everything together until well incorporated.

Line a loaf pan with parchment paper and press the combined chickpea mixture into the pan, smoothing the top with a spatula.

In a small bowl, whisk together the tomato sauce, maple syrup, and balsamic vinegar for a glaze. Spread the glaze over the top of the meatloaf.

Preheat your oven to 350°F (175°C) and bake for 60 minutes, until the top is golden brown. Let it cool in the pan for 15 minutes before slicing.