Strain the canned beans, wash them, and let them drain really well. Mix the flaxseed with hot water in a small bowl and set aside until it becomes thick.
Add olive oil to the pan and saute diced onions and mushrooms over medium heat Cook until everything becomes soft and brown, about 8-10 min. Set aside.
Briefly grind the walnuts and oats in the food processor.
Add fresh parsley leaves, spices, beans, sauteed mushrooms, onions, and flaxseed egg, and pulse everything briefly (5-6 seconds). You don't want to overdo otherwise the mixture will become mushy.
Dip your fingers in some water and shape the patties. Each should weigh between 120-130 g and be about 8 cm (3.14 in) in diameter.
On a clean, well-heated pan, add olive oil and bake the patties for about 3-4 minutes on one and 3-4 minutes on the other side until they become crispy.
Place on a plate lined with kitchen paper, to absorb the excess oil and serve warm!