Mash the banana: In a bowl or jar, mash a ripe banana until mostly smooth.
Some small chunks are fine.
Whisk in wet ingredients: Add 1/2–3/4 cup milk, 1–2 tablespoons peanut butter, 1–2 teaspoons maple syrup or honey (optional), 1/2 teaspoon vanilla (optional), and a small pinch of salt. Whisk until the peanut butter is well incorporated.
Add the dry ingredients: Stir in 1/2 cup rolled oats and 1 teaspoon chia seeds (optional). If using Greek yogurt, add 1/4 cup now for extra creaminess.
Adjust thickness: The mixture should look pourable but not watery.
If it’s very thick, add a splash more milk. If it’s thin, a bit more oats or chia will help.
Chill: Cover the jar or bowl and refrigerate at least 4 hours, but overnight is best for full hydration and creaminess.
Stir and top: In the morning, give it a good stir. Add sliced banana, a drizzle of peanut butter, chopped peanuts, cinnamon, or cacao nibs.
Serve: Enjoy cold straight from the fridge, or warm gently in the microwave with a splash of milk if you prefer it cozy.