Toast the pecans: Add chopped pecans to a dry skillet over medium heat for 3–5 minutes, stirring often, until fragrant. Set aside to cool.
Mix wet ingredients: In a medium bowl or jar, whisk milk, Greek yogurt, maple syrup, vanilla, cinnamon, and a pinch of salt until smooth.
Add protein powder: Whisk in the protein powder until fully dissolved. If it clumps, let it sit 2 minutes, then whisk again.
Stir in chia seeds: Sprinkle chia seeds over the mixture and whisk well so they don’t clump at the bottom.
Rest and whisk again: Let the mixture sit for 10 minutes, then whisk once more to redistribute any settling seeds.
Chill to thicken: Cover and refrigerate for at least 2 hours, preferably overnight, until thick and pudding-like.
Serve: Stir, taste for sweetness, and adjust if needed.
Top with toasted pecans and any optional toppings. Enjoy cold.