In a medium-sized mixing bowl, combine the Greek yogurt, vanilla protein powder, honey (or maple syrup), and vanilla extract. Use a whisk or a spatula to stir until the mixture is completely smooth and the protein powder is fully incorporated. Make sure there are no dry clumps of powder left.
Line a large baking sheet with parchment paper or a silicone baking mat. Pour the yogurt mixture onto the center of the sheet. Using a spatula, spread the yogurt evenly until it is about 1/4 to 1/2 inch thick. Try to create a rectangular shape to make breaking it into pieces easier later.
Arrange the thin peach slices across the surface of the yogurt. You can lay them in rows or scatter them randomly for a rustic look. Press them down very gently so they are slightly embedded in the yogurt.
Evenly distribute the granola over the top of the yogurt and peaches. Finish by lightly dusting the entire tray with ground cinnamon. This adds warmth and mimics the flavor of a baked peach crumble.
Place the baking sheet flat in your freezer. Let it freeze for at least 3 hours, or until the yogurt is completely firm and solid to the touch. Avoid moving the tray during the first hour to ensure an even set.
Once frozen, remove the sheet from the freezer. Lift the parchment paper and break the bark into irregular pieces using your hands, or use a sharp knife to cut it into clean squares. Serve immediately while still frozen.