Line 2 shallow baking trays with foil. Preheat your oven to 375 F. Trim as much excess fat and loose skin off the chicken as you can.
In a large mixing bowl, combine the olive oil, vinegar, fish sauce, soy sauce, kosher salt and white pepper. Add the chicken and toss to coat the meat. Let sit for about 5 minutes, then shake the marinade off the chicken and lay 6 pieces into each baking tray.
Add the asparagus, mushrooms and leek to the marinade and toss to coat. Scatter the veg into the trays, around the chicken pieces. Try to keep everything in a single layer. Pop the trays into the oven and bake for 30 minutes.
Pull the trays from the oven and remove the chicken. Use a spoon or spatula to swirl the mushrooms, veg, and pan juices around. Return the chicken pieces to the pans and put them back in the oven, rotating the pans as you do so. Bake another 20 to 30 minutes until done.