Preheat oven to 300ºF. Plug in a waffle maker.
While the waffle maker is heating up, stir together the pancake/waffle mix, milk, egg and oil a large mixing bowl, making sure not to overmix. Toss in the ham and cheese and give it a stir to combine.
Once the waffle maker is hot, brush it lightly with some melted butter, then ladle about 1/4 cup of batter into the center. Close the lid and cook until the waffles are golden brown and steam has stopped coming out from between the griddle plates, 3-4 minutes.
Place the finished waffles onto a baking sheet lined with a cooling rack and reserve them in the warm oven while you finish cooking off the rest of your batter.