Mash the fruit base: In a bowl, mash the banana with a fork until mostly smooth. Add the sliced strawberries and lightly mash, leaving some small chunks for texture.
Stir in the wet ingredients: Add the milk, Greek yogurt, vanilla, sweetener (if using), and a pinch of salt.
Whisk until the mixture is smooth and well combined.
Add chia seeds: Sprinkle in the chia seeds and whisk well to distribute evenly. This helps prevent clumping.
Let it thicken: Let the mixture sit for 10 minutes, then whisk again to break up any settling seeds.
Chill: Cover and refrigerate for at least 2–3 hours, or overnight for best texture. It should set to a thick, pudding-like consistency.
Adjust: If it’s too thick, stir in a splash of milk.
If it’s too thin, mix in 1 more teaspoon of chia seeds and chill 15–20 minutes.
Serve and top: Spoon into jars or bowls. Add fresh strawberry slices, banana, a sprinkle of granola, or a drizzle of almond butter for crunch and flavor.