Sauté onions, garlic, mushrooms and basil until soft and starting to brown.
Remove from heat. Cool slightly.
In large bowl mash lentils coarsely (potato masher works well), stir in egg, cooked mushroom, mixture, rolled oats, Parmesan cheese, nuts, salt and pepper to taste.
Shape into four (3/4 inch/2 cm thick) patties
Cook patties in lightly greased non-stick fry pan or on a greased grill over medium-high heat, 3-4 minutes per side or until golden brown.
Serve with choice bun or on lettuce with favourite toppings (e.g.: sautéed mushrooms, blue cheese, red onion, avocado, etc)