Blend the banana, applesauce, chia seeds, and vanilla essence together in a blender until completely smooth.

In a mixing bowl, whisk together the rolled oats, flour, cinnamon, and baking powder until evenly combined.

Add the blended wet ingredients and melted butter to the dry ingredients. Stir to combine. The dough will be quite wet—this is normal.

Cover the bowl and refrigerate the dough for 10–20 minutes. This gives the chia seeds time to gel and the butter time to firm up, making the dough much easier to handle.

Preheat your oven to 180°C (360°F). Line a baking sheet with parchment paper.

Using a damp spoon or cookie scoop with damp hands, scoop the dough into balls and place on the lined baking sheet. Flatten gently with the back of a damp spoon to about ½ inch thick.

Bake for 10 minutes until the edges are lightly golden. Do not overbake—cookies will firm up and harden as they cool.

Transfer to a wire rack and cool completely before serving or storing.