Preheat the oven to 180 C / Gas 4. Grate halloumi cheese.
Wipe baking tray with olive oil. Then lay down a thin layer of filo pastry. Sprinkle mix on top. Continue layering until the mushroom cheese mixture and the filo are used up, about 12 layers. Brush top with olive oil.
Bake in the preheated oven until golden, about 12 minutes.