In a bowl, mix together the yogurt, honey, collagen (if using), and 1/4 cup of cocoa powder until smooth.
Add the remaining 1/4 cup of cocoa powder and mix until no lumps remain.
Line a baking sheet with parchment paper and spread the yogurt mixture evenly on top.
Microwave the peanut butter and coconut oil for 30 seconds until drippy, then drizzle it evenly over the yogurt.
Add the pretzels on top and freeze for at least 8 hours or overnight until solid.
Once frozen, break the bark into smaller pieces using your hands or a rolling pin.
Store any leftovers in the fridge for up to one week or in the freezer for up to one month. Enjoy!