Add the milk and yogurt to the blender first. This helps the blades catch the fruit easily.
Add strawberries, banana, chia or flax (if using), vanilla, and sweetener (if needed).
Blend on low, then increase to high until completely smooth, 30–60 seconds.
If it’s too thick, add a splash more milk.
Taste and adjust sweetness. If your berries are very ripe, you may not need any added sweetener at all.
Serve immediately in a small cup with a straw or a spill-proof cup. For very young toddlers, pour into a silicone straw cup for easier sipping.