Cut the onion into cubes and fry in a little oil with the mince until crumbly, then remove from the heat. Chop the cheese and olives and stir in. Season well with salt, pepper and rosemary.
Put 1 - 2 tablespoons of the filling on each puff pastry disc, fold the disc and press it into place at the edges. Brush the surface with beaten egg and sprinkle with rosemary.