Tuna Panini Melt

Yes. Cook it in a skillet over medium heat and press it down with a second heavy pan, turning once, until both sides are crisp and the cheese has melted. That takes a little longer than the 3 to 4 minutes a press needs, since only one side is heated at a time.

Yes, but drain it very well. This already has a tablespoon of mayonnaise in it, and oil-packed tuna adds more fat on top of that, which can make the filling greasy inside a pressed sandwich.

The tuna was not drained enough. Press the liquid out of the can properly before mixing, since the balsamic vinegar and mayonnaise add moisture of their own and sourdough will absorb whatever is left while it cooks.

Cheddar, Swiss or provolone all work. American cheese is used because it melts very smoothly at the low heat of a press, so a firmer cheese may need an extra minute to melt through.

Yes, mix the tuna, mayonnaise, balsamic vinegar, onion and pickle and keep it covered in the fridge. Assemble and press the sandwiches only when you are ready to eat, or the bread will soften.

Sourdough is what this uses and it suits a press well, since a firm open crumb crisps rather than compacting. Any sturdy bread works, but avoid very soft sliced white, which flattens to almost nothing under a press.