Thaw the puff pastry according to the package instructions. Preheat the oven to 425 degrees and line a baking sheet with parchment paper - you may need to use 2 baking sheets.
Combine all of the cream cheese ingredients in a bowl and mix to combine. I like to thin mine with non-dairy cream, but that isn't necessary. Set aside.
Use a mandoline to thinly slice the potatoes. Add them to a bowl with the vegan butter, dry seasonings and rosemary. Toss to coat evenly and set aside.
Lay one sheet of puff pastry out on a clean surface and cut into 4 squares. Place the squares on the prepared baking sheet and repeat with the other sheet of puff pastry. Use a knife to create a 1/2" border around each square – being sure not to cut all the way through. Use a fork to score the inside rectangle of the dough. Add some of the cream cheese mixture to the center portion of each square and spread to the edges. Top with a layer of potatoes. Sprinkle some salt and more rosemary over the potatoes.
Fold the corners of each square in slightly - if you have trouble getting the corners to stick just brush the underside with some of the cream cheese mixture. Brush the edges of the dough with vegan butter and place in the oven for 20-25 minutes, or until the dough is crispy and the potatoes are cooked through.