Take a sheet of puff pastry. Put it to bake until puffed, but not reddened. Using a sharp knife, cut a square about 3/4″ (2 cm) from the edge, but only from the top. You should get something like a square boat with a bottom and a side wall, which will not allow the filling to leak out.
Smear the puff boat with tomato paste, place the sausages on top and arrange plump slices of cheese close to each other. Distribute slices of tomato on top and sprinkle with oregano. Bake the puff pastry pizza in a hot oven until the cheese gets a nice tan.
Serve slightly cooled with some chopped parsley.