Bring a pot of salted water to a boil and cook cubed sweet potato for 10 minutes or until pieces are cooked through and tender.
While sweet potatoes are cooking, make the dough by combining all-purpose flour with sea salt. Then add water and oil and fold until just combined.
Place the dough onto a lightly floured surface and knead until it comes together and is slightly sticky, but not sticking to your hands too much. Lightly flour the ball of dough. Cut it in half and wrap each smaller ball of dough in plastic wrap. Refrigerate the dough while you prepare the filling.
Drain the sweet potatoes and mash until very smooth with the filling ingredients, except sauerkraut. Stir in the sauerkraut after mashing and mixing the sweet potato mixture. Refrigerate until ready to fill pierogi.
If you’re cooking the pierogi immediately, bring a large pot of salted water to a boil while you roll, cut, and fill the pierogies.
On a lightly floured surface, roll out one ball of dough until it is 1/16-inch thick. Use a 3 ½ to 4-inch round cookie cutter and cut out rounds of dough. Place each one onto a lightly floured baking sheet or tray, and cover with a tea towel while you continue to roll dough and cut out rounds. Do the same with the other ball of dough.
Place ½ to ¾ tablespoons of sweet potato filling on one side of each round of dough. Have a small dish of water standing by. Using a finger, dab a little water on the edge of half the circle, fold the other side of dough over the filling and gently press and slightly pinch the two sides together sealing the pierogi. Set each pierogi back onto the floured baking sheets or trays without over lapping. If you want to freeze them at this point, make sure they’re lightly floured on the outside to prevent sticking and place them between layers of parchment paper.
Boil pierogi in small batches for 1 to 2 minutes until they float to the surface. Remove them from the water with a slotted spoon and set aside onto a baking sheet or plate.
Right before serving, fry pierogies in batches in a pan over medium heat with vegan butter for approximately 2 to 3 minutes each side until golden brown.
Serve with vegan sour cream or try the hot for food cashew sour cream, as well as caramelized onions, and/or fried mushrooms!