Place the banana in a quart-size resealable plastic bag. Seal the bag and mash the banana with your hands until smooth, working out the big lumps.
Open the bag and add the flour, baking powder, egg, and milk or water. Reseal the bag, squeezing out the air, then knead and squish the bag until all ingredients are combined into a smooth batter. If it's too thick, add another tablespoon of milk or water.
Snip a small corner off the bottom of the bag (about 1/2 inch). This creates a piping bag for easy, clean dispensing.
Heat a camp stove to medium heat and place a non-stick pan or griddle on it. Add the butter or oil and let it melt, tilting the pan to coat the surface.
Pipe the batter directly from the bag onto the hot pan, forming 3- to 4-inch circles. Cook until bubbles form on the surface and the edges look set, about 2 minutes. Flip and cook another 1-2 minutes until golden brown.
Repeat with remaining batter, adding more butter or oil as needed. Serve warm with maple syrup or honey.