In a medium bowl, whisk the milk and collagen until dissolved. Add chia seeds, vanilla extract, and honey (if using) and whisk until combined. Cover and refrigerate overnight (or at least 6 hours), stirring at least once to ensure it's clump-free.
The next morning, spoon the chia seed pudding into a serving dish. Top with mango and serve. You can also mix the mango in the night before for quicker prep.