Place the meat portions in a mixing bowl. Season with salt and pepper, drizzle with the olive oil and lemon juice and add the oregano, fresh mint and garlic cloves, cut in thin slices. Give everything a good toss and add the bay leaves. Cover and leave in the fridge for 2-3 hours, tossing occasionally. Cut the potatoes in round slices. Sir fry them in a pan with olive oil, over low heat, for 10 minutes until they soften. Transfer in a platter.Spread all six greaseproof paper sheets on a working surface. Place in the centre of each 3-4 potato slices, put a meat portion on top and finish with a slice of kefalotiri cheese. Drizzle with 2 tablespoons of the marinade and fold the greaseproof paper over the meat (seam side down). Place all six bags on a flat metal baking tray and bake them in a preheated oven at 180º C for 1 hour and 15 minutes.