Preheat oven to 400 degrees.
Make your flax egg by mixing flax and water, let sit refrigerated for 10-30 minutes.
Heat oil in a skillet over medium heat. Add onions and garlic and cook for 5 minutes. Add mushrooms, cilantro, spices, soy sauce and balsamic and cook or 5 more minutes.
Combine cooked lentils with mushrooms, onions, flour, oats, egg, salt/pepper, and olive oil.
Form burgers 5-6 evenly sized burgers out of about ½ cup or one small handful of mixture on a lined sheet pan. The dough is pretty sticky so I recommend working with wet hands.
Bake burgers for 30-35 minutes on a lined or greased sheet pan.
Serve with a toasted bun and toppings of choice.