Add the strawberries to a blender with the raspberries, milk, maple syrup, and vanilla extract. Blend until completely smooth.
Pour the strawberry milk into a medium container or shallow baking dish. Add the chia seeds and a pinch of salt. Whisk thoroughly to combine.
Cover and refrigerate for at least 4 hours, or overnight. After chilling, stir again to break up any clumps.
Spoon into bowls or jars and top with Greek yogurt, nuts, crushed freeze-dried strawberries, or fresh fruit as desired. Keeps well in the refrigerator for up to 5 days.