In a large bowl, use a fork or whisk to mix together the whole wheat flour, sugar, baking powder, baking soda, and salt.
Add the yogurt, milk, egg, and vanilla extract. Whisk the batter just until combined, taking care not to overmix. If you have big lumps, use a rubber spatula to squish them to the side of the bowl instead of mixing too vigorously. Some lumps are ok. (If you don’t mind dirtying two bowls, you can whisk the wet ingredients in a separate bowl first, then fold into the dry ingredients.)
Fold the melted butter into the batter until just combined. Let the batter stand for 5 to 10 minutes. It will thicken slightly.
Heat your cast iron skillet over medium heat. Add a small pat of butter. You know the pan is ready when the butter sizzles right when you add it to the pan. If it browns quickly, reduce the heat. Pour in ½ cup of batter for each pancake. Cook until the bottom is browned and bubbles form on the top of your pancake, particularly in the center, about 2 to 3 minutes. Flip the pancake and cook until it springs back when pressed in the center (about 2 minutes). Repeat with the remaining batter.
Notes
To add fruit to these pancakes, dot the fruit on the pancakes right after you put the batter in the pan. Then cover with a little more batter. Blueberries, strawberries, chopped peaches, or chopped bananas are tasty additions!
Whole wheat pancakes cook up slower than all-purpose flour pancakes so make sure that plenty of bubbles have formed on the surface of the pancake before you flip it. Flip only once for maximum fluffiness and the best results!
You can freeze the pancakes in freezer bags after they have cooled. They reheat nicely in the microwave.