Whisk the flour, sugar, baking powder, baking soda, and salt in one bowl.
Whisk the buttermilk, eggs, melted butter, and vanilla in another bowl.
Pour the wet ingredients into the dry ingredients.
Stir until combined.
Leave a few lumps in the batter.
Heat an ebelskiver or appe pan over medium-low heat.
Brush each well lightly with oil or melted butter.
Let the pan warm for a minute or two before adding batter.
Fill each well about two-thirds full with batter.
Add a few tiny mix-ins, if using.
Cook for 1 to 2 minutes, until the edges start setting.
Use a skewer or small spoon to turn each popper halfway.
Let the uncooked batter flow into the well as you turn it.
Continue turning until each popper becomes round and golden.
Cook another 2 to 3 minutes, until fully puffed and set.
Move the finished pancake poppers to a plate.
Repeat with the remaining batter.
Serve warm with maple syrup, powdered sugar, fresh fruit, whipped butter, or other toppings listed above.