Arrange the frozen strawberries and banana in a blender, then pour in the milk and add the yogurt. Blend thoroughly until the mixture reaches a smooth, creamy consistency, incorporating extra milk gradually if a thinner texture is desired. Pour into glasses and serve at once. Any remaining smoothie may be poured into ice cube trays and frozen for later use.
Notes
To achieve a thicker texture, reduce the amount of milk. Optional enhancements include adding chia seeds or a drizzle of honey to taste.