Toast the pinenuts in a dry pan until they are browned.
Put the green olives in a blender, so you get a rough textured paste. Season it with some salt and a pressed garlic clove. Then ad the Pecorino cheese, the toasted pinenuts and the parsley. Mix this all up.
Put a pan on the fire, add some olive oil and brown the sliced mushrooms. Put a little salt and pepper in and bake it a couple of minutes more before taking them out.
Put a little bit more olive oil in the pan and sliced onions. Fry them till they are soft and browned.
Mix the mushrooms, onions and tapenade and keep it aside while you prepare the picanha.
Take a chefs knife and make a pocket in the picanha beginning by the flat side of the triangular shape. Make sure not to pierce through the other sides.
Put the stuffing in the pocket you’ve made. Get as much as possible in as you can.
Carve the fat cap so it can render down more easily. Sprinkle a bit of salt on top.
Fire up your grill to an indirect temperature of 140°C/284°F. Put the picanha on the cooler side of the grates and stick a thermometer in the meat without hitting the stuffing.
Close the lid and let the picanha cook to a core temperature of 50°C/122°F Before you sear it over direct heat to form a nice crust.
Let the picanha rest for 10 minutes and cut it into thick slices.