Oh my yes, a Francesinha is an amazing sandwich!
The Pestana Porto makes a good one, but I can't judge it relative to any others because that's the only one I've had.
You better be hungry, though!
From bottom to top: bread, beefsteak, sausage, cheese, bread, country ham, a different sausage, a different cheese, more bread, special sauce, and finally more cheese! Served hot with the top layer of cheese nicely toasted. The ones we had were basically cubes the size of a slice of bread, and they were heavenly!