Preheat oven to 180 C (355 F) and line a loaf tin with baking paper.
Mash banana in a mixing bowl.
Add egg and milk, mix with a whisk or a fork until well combined.
Add flour, mix until it becomes a smooth batter.
Add vanilla and chia seeds and stir through.
Pour into prepared loaf tin and smooth out the top.
Bake for approximately 30-35 minutes, until golden on top and a toothpick inserted into the center comes out clean.