Whisk the base: In a bowl or jar, whisk the milk, cocoa powder, sweetener, vanilla, and salt until the cocoa is fully dissolved and smooth.
Add protein (optional): Stir in Greek yogurt and/or protein powder until well combined.
If it’s too thick, add a splash more milk.
Stir in chia seeds: Sprinkle in the chia seeds and whisk for 30 seconds so they don’t clump.
Set, then stir again: Let the mixture rest for 10 minutes, then whisk again to break up any settling seeds.
Chill: Cover and refrigerate for at least 2–3 hours, or overnight, until thick and pudding-like.
Serve: Stir, then layer or top with fresh berries. Add optional toppings like nuts or dark chocolate.