Back jacket potatoes, according to number of people to eat it (although in your case, you may want to go extra as they'll keen in the fridge just fine and are fine microwaved for easy left over lunch the next day).
Once cooked, cut in half lengthways and scoop out the potato flesh into a mixing bowl. Add tuna and philly to the mixing bowl (quantities are up to you but I would usually go for one tin of tuna for 3 medium potatoes or 2 huge ones and about half a tub of cream cheese).
Mix energetically. Add salt and a very generous grinding of black pepper (I tend to add what I think is a lot of pepper... then grind in a bit more).
Put the mixture back into the potato skins and top with grated cheese. Then pop back into the oven until the cheese is melted and the potatoes are cooked through.
[if cooking more than you need, don't reheat the ones you're going to eat the following day - rather leave them and then put them in oven or microwave when you're ready to eat).