1 Place the mushroom caps, smooth side up, in a shallow dish.
2 Whisk together the vinegar, oil, garlic and salt and pepper to taste. Pour over the mushrooms and leave to stand for 15 minutes, turning twice.
3 Heat the broiler (grill)
4 Toast the burger buns and set aside.
5 Place the mushrooms on the broiler, reserving the marinade for basting. Grill for 5-8 minutes on each side, until tender, brushing with the marinade frequently.
6 For the salsa: put the garlic, egg yolks and mustard into a food processor or blender. Blend into a paste and very slowly drizzle in the olive oil to make a thick mayonnaise-like sauce.
7 Add the lemon juice and season to taste with salt and pepper.
8 Place a few salad leaves on the base of each burger bun. Top with a mushroom cap, smooth side down.
9 Spoon some salsa on each mushroom cap. Garnish with mango strips, chilis and bean sprouts.