Preheat oven to 350F
Make a flax egg by mixing 1tbsp ground flaxseed with 2.5 tbsp water in a small bowl. Let sit for 5 minutes to thicken.
Chop yellow onion, garlic and cremini mushrooms. Heat 1 tbsp olive oil in a pan on medium heat, sauté until soft. About 5 minutes.
Once vegetables are soft add to food processor along with lentils, breadcrumbs, fresh parsley, flax egg, and salt + pepper. Pulse ingredients until combined.
Roll each ball between your hands to form golf-ball sized balls. Place evenly spaced on a lightly greased baking sheet.
Bake in pre-heated oven for 25-30 minutes. Rotate each ball every 10 minutes. (The longer you leave them in the oven, the crispier the outside will become)