Rinse and drain your lentils and chick peas. Drain them well because we want to avoid excess water. Transfer all ready to blend ingredients into your food processor. Cut the mushrooms and onions and fry them at medium heat until they start turning brown. Add pepper if you like. Deglaze with some Soy sauce and stir well. Continue frying until the soy sauce is gone.Into the blender with that stuff as well.
Preheat the oven at 200° C (392° F). Blend the mass at medium speed until all ingredients become smooth and sticky. You still should be able to see bits of the oats and legumes, but overall it should be meat-like and sticky.Let the mass rest for about 10 minutes to let the flax seeds do their magic and bind. Start forming patties on a baking tray with parchment paper. Bake them for 5 minutes on each side. It is okay if the patties start getting some dark spots, but don't burn them to the ground.
The freezer way
Let the patties fully cool down. Place them in a container, separated by some parchment paper and put them in the freezer.When hungry, take a frozen pattie and fry them on low to medium heat. Due to their low fat contents, they might turn dark faster than meat patties or convenience food burgers.
Add them into a pre-heated pan with some (really just some) oil. Fry them on both sides for about one minute each.