Mix yogurt, protein powder (if using), milk, sweetener, cashew butter, and seeds together until smooth
Line sliced berries in popsicle molds, then pour mixture into the molds
Place your popsicle sticks in the center, and freeze at least 3 hours
These will keep ~ 1 week in the freezer, so yes you can prep them ahead of time!
Notes
Can omit the flaxseed or cashew butter (just adds to the creaminess) can use pure maple syrup in place of honey can use dairy free protein if needed, just note it won't be as high in protein.