Put the rinsed lentils, peeled onion, potato and carrots in a large pot. Add enough water to cover generously. Bring to a boil, reduce to a gentle simmer and partially cover. Cook for about 40 minutes, checking from 30 minutes, until the lentils and the centers of all the vegetables are very soft. Add hot water as needed to keep everything submerged. Larger vegetables and older lentils may take longer. Optional but recommended for quicker, more even cooking: dice the vegetables into roughly 1 cm pieces first. Start checking after 25 minutes, but continue until everything is fully tender.

Drain thoroughly in a fine mesh strainer and leave for 5 minutes. Return to the pot. If water still collects at the bottom, stir over low heat briefly to evaporate it. Mash the vegetables completely and crush most of the lentils, leaving a little texture. Let cool for about 15 minutes, until comfortable to handle.

Add the breadcrumbs, parsley, Italian seasoning, garlic powder, paprika, salt, pepper and 2 tablespoons of olive oil. Mix thoroughly, then rest for 10 minutes so the crumbs absorb moisture. Squeeze a small portion: it should hold together without slumping. If wet, add breadcrumbs 1 tablespoon at a time and rest again. If crumbly and dry, mash more thoroughly and add water 1 teaspoon at a time.

Heat the oven to 200°C conventional / 180°C fan / 400°F. Line two baking sheets with parchment. Divide into about 32 equal portions and compress firmly into balls. Arrange with space between them and brush with the remaining tablespoon of olive oil.

Bake for 30 to 40 minutes, until browned outside and firm enough to lift. Carefully turn after a crust has formed, around halfway through, and swap the trays between racks. If a ball resists lifting, give it a few more minutes before turning. Let stand for 5 to 10 minutes after baking to firm up.

Warm the marinara in a wide pan and stir in the basil. Taste before adding more salt or pepper. Gently fold in only the meatballs you plan to serve, just long enough to coat and heat through. Work in batches if necessary. Avoid prolonged simmering or vigorous stirring, which can soften and break them.

Serve with pasta or make the pesto subs described in the notes. For each sub, lightly toast a roll, spread with vegan ricotta or cream cheese and pesto, then add 4 meatballs with sauce. Finish with optional vegan parmesan and serve straight away.