Mash the banana: In a medium jar or bowl, mash the banana until mostly smooth. A few small chunks are fine and add texture.
Add wet ingredients: Stir in the milk, Greek yogurt, vanilla (if using), and sweetener.
Mix until well combined.
Whisk in protein: Sprinkle in the protein powder gradually, whisking to avoid clumps. If it gets too thick, add a splash more milk.
Stir in dry ingredients: Add oats, chia seeds, and a pinch of salt. Fold in the diced strawberries last so they don’t break down too much.
Adjust consistency: The mixture should be pourable but thick.
If it’s very dense, add 1–2 tablespoons of milk and stir again.
Chill: Cover and refrigerate for at least 4 hours, ideally overnight, to let the oats soften and the chia seeds gel.
Before serving: Give it a good stir. If it’s too thick, loosen with a splash of milk. Top with extra strawberries, banana slices, and a drizzle of nut butter if you like.
Enjoy cold or slightly warmed: Eat it straight from the fridge, or warm gently in the microwave in 15–20 second bursts, stirring in between.
Add fresh fruit after warming.