Take out the dough to thaw to room temperature or until pliable, about 50 minutes.
Prepare chia jam. Once cooled, blend until smooth in a blender or food processor.
Preheat oven to 350 degrees.
Using a pizza cutter or sharp knife, cut each sheet into 6 equal rectangles.
Place 6 rectangles on a parchment lined baking sheet. Top each with about 2 tbsp of jam. Cover each with the other 6 rectangles and use a fork to crimp around the edges.
Brush tops with water and transfer to oven to bake for about 18-22 minutes or until golden brown.
In the meantime, make the icing by combining all ingredients in a bowl until smooth.
Once poptarts are done baking, transfer to a wire rack to cool. Spoon on icing and let set for a couple minutes before enjoying!