Preheat oven to 425°F. Spray a 9 x 13-inch baking dish with cooking spray and set aside.
In a large bowl, stir together pancake mix, buttermilk, milk, egg, oil, cinnamon, and vanilla extract. Fold in the apples. The batter will still be a little bit lumpy (and that’s fine) – don’t overmix or the pancakes will be dry.
Pour batter into the prepared baking dish.
Bake, uncovered, for about 12-15 minutes, or until cooked through in the center.
Slice into squares and serve with desired toppings!
Notes
Do not over-mix the batter. Stir just until the ingredients are combined. You will still have some lumps, which is fine. Over-mixing will result in dense, tough, and dry pancakes.
If time allows, let the batter rest for 5-10 minutes. This gives the leavening agents extra time to react, which results in puffier, fluffier, light pancakes.
The total baking time will vary. If using a glass dish, the pancakes will need closer to 15 minutes in the oven. Metal or dark nonstick pans only require about 10-12 minutes. The pancakes are done when a toothpick inserted in the center comes out clean.
Slice the pancakes into 8 large rectangles or 16 smaller squares. Some readers have even suggested using cookie cutters to cut out fun pancake shapes for your kids!