1. Cook the Lentils:
* Combine the rinsed lentils and vegetable broth (or water) in a medium saucepan.
* Bring to a boil, then reduce heat to low, cover, and simmer for 20-25 minutes, or until lentils are tender but not mushy. They should still hold their shape.
* Drain any excess liquid very well. Set aside to cool slightly. This step is crucial; excess moisture can lead to mushy meatballs that don’t hold together.

2. Sauté the Aromatics:
* While lentils are cooking or cooling, heat the olive oil in a large skillet over medium heat.
* Add the finely chopped onion and grated carrot. Sauté for 6-8 minutes, stirring occasionally, until softened and the onion is translucent.
* Stir in the minced garlic and cook for another 1-2 minutes until fragrant. Be careful not to burn the garlic.
* Add the tomato paste to the skillet. Cook for 1-2 minutes, stirring constantly. This step caramelizes the tomato paste slightly, deepening its flavor.
* Remove from heat and let the mixture cool slightly.

3. Prepare the Walnuts (if not already chopped):
* If you haven’t already, finely chop the walnuts. For a finer texture, you can pulse them a few times in a food processor until they resemble coarse crumbs. Be careful not to over-process into nut butter. Toasting them lightly in a dry pan before chopping can enhance their flavor.

4. Combine Wet and Dry Ingredients:
* In a large mixing bowl, combine the cooked and drained lentils, the sautéed onion-carrot-garlic mixture, finely chopped walnuts, panko breadcrumbs, Italian seasoning, smoked paprika, fresh parsley, salt, and pepper.
* If using a flax egg, prepare it now and add it to the bowl. If using a regular egg, lightly whisk it in a small separate bowl before adding.
* Add the soy sauce (or tamari).

5. Mix the Meatball Mixture:
* Using your hands or a sturdy spoon, mix all the ingredients together until just combined. Be careful not to overmix, as this can make the meatballs tough. The mixture should hold together when pressed.
* Taste Test (Optional but Recommended): If you’re comfortable doing so (and not using a raw egg, or by cooking a tiny patty), taste a small amount of the mixture and adjust seasonings if necessary. This is your last chance to perfect the flavor.

6. Chill the Mixture (Optional but Recommended):
* Cover the bowl and refrigerate the mixture for at least 15-30 minutes. Chilling helps the ingredients meld and makes the mixture easier to handle and roll, leading to firmer meatballs.

7. Form the Meatballs:
* Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper for easy cleanup.
* Using slightly damp hands (to prevent sticking), take about 1.5-2 tablespoons of the mixture and roll it into a firm, compact ball, about 1.5 inches in diameter.
* Place the formed meatballs on the prepared baking sheet, ensuring they are not touching. Repeat with the remaining mixture. You should get about 20-24 meatballs.

8. Bake the Lentil Meatballs:
* Bake for 20-25 minutes, or until the meatballs are nicely browned, firm to the touch, and slightly crispy on the outside. You can flip them halfway through for more even browning if desired.
* Alternative Pan-Frying Method: For an extra crispy exterior, you can pan-fry the meatballs. Heat a tablespoon or two of olive oil in a large non-stick skillet over medium heat. Add the meatballs in a single layer (work in batches if necessary) and cook for 5-7 minutes, turning occasionally, until browned on all sides. You can then finish them in the oven as above for a few minutes to ensure they are heated through, or if they are smaller, they might cook through entirely in the pan.

9. Serve and Enjoy:
* Your delicious Vegetarian Lentil Meatballs are ready! Serve them warm with your favorite marinara sauce over pasta, in subs, or as desired.