Finely chop the onion, garlic and mushroom.
Heat a spoonful of oil in a pan and gently sauté the onion for 5 minutes. Add the mushroom, garlic and herbs, then cook for 8-10 minutes, under cover, until the mushroom has released all its liquid and browned. Turn up the heat and let the liquid evaporate. Let it cool. Chill this mixture until you’re ready to cook the patties.
Add the mushroom mixture and the rest of the ingredients to the mince. Season with salt and pepper to your liking, then combine well.
Divide the mixture into 4-6 equal portions, then form balls and flatten them between your palms to create patties.
Using a large frying pan or cast iron griddle, cook the burgers for 10 minutes or so, turning once, until evenly cooked. Alternatively, brush them with oil and grill or barbecue them over medium heat.
While the burgers are cooking – prepare the buns, salad and condiments of your choice. ( You might want to toast the buns).
Serve the burgers immediately.