Make Fathead according to recipe adding 1 tsp garlic powder and salt. Roll into a rectangle shape.
Spray a rectangular tart pan with olive oil. Line with Fathead and press down around the edges to cut off the excess. Prick the bottom of the Fathead with a fork all over and bake for approximately 5 minutes.
Meanwhile, heat butter in frying pan over high heat and add mushrooms. Sauté until cooked. Add oregano, salt and pepper and mix through. Place mushrooms over pastry in tart pan on a layer. Sprinkle and top with chopped mint.
Whisk together eggs and cream and very gently and slowly pour over the mushrooms. Let it fill all the nooks and crannies before adding more or it could spill over the sides of the pastry. Top with crumbled feta.
Bake at 180C for approximately 18 minutes until set and feta is golden. Allow to cool in pan until cool enough to handle then remove and serve. If not serving straight away, cool on a wire rack to prevent the Fathead becoming soggy.