Heat the oven to 200 C / 400 F. Line a sheet pan (33 x 46 cm / 13 x 18 inch) with parchment paper and brush lightly with olive oil.

Heat 1 tablespoon of olive oil in a 12-inch nonstick skillet over medium heat. Add the diced onion and cook for 4 to 5 minutes until soft and translucent. Add the garlic and cook 1 minute more until fragrant. Take off the heat and let cool slightly.

In a large mixing bowl, mash the lentils with a potato masher or fork until mostly broken down but still a little chunky. Mashing them into a smooth paste is the fastest way to end up with mushy meatballs that won't hold their shape.

Add the ground oats, egg, cooked onion and garlic, cumin, smoked paprika, coriander, cinnamon, salt, pepper, parmesan, and parsley to the lentils. Mix with a fork or your hands until fully combined and the mixture holds together when you press a spoonful between your fingers.

Let the mixture sit for 5 minutes so the oats can soak up moisture. This makes a real difference in how well the balls hold together.

Scoop the mixture into 35 g portions, about 2 tablespoons each, and roll into balls between your palms. You should get about 16 to 18 meatballs.

Arrange the balls on the sheet pan, leaving a little space between each. Drizzle the tops with the remaining 1 tablespoon of olive oil.

Bake for 20 to 22 minutes, flipping each meatball gently halfway through, until golden brown on the outside and firm when pressed.

Cool on the pan for 5 minutes before serving. They firm up more as they cool, so don't worry if they feel slightly soft straight out of the oven.