In a bowl, mix the chia seeds, milk, vanilla yogurt, vanilla extract, espresso, and sweetener of choice. Stir well to combine.
Cover and let it sit in the fridge for at least 2 hours (or overnight) until thickened. Stir once halfway through to prevent clumping.
Once set, give the pudding a final stir and serve it in a cup.
Spread a layer of vanilla yogurt on top, then sift cocoa powder over it for a classic tiramisu touch.