In a large bowl, whisk together the all-purpose flour, pea protein powder, and sea salt until well combined.
Gradually add the water to the dry ingredients, kneading by hand for about 5 minutes until a smooth, elastic dough forms.
Cover the dough with a clean cloth and let it rest for 15 minutes to allow the protein to fully hydrate.
While the dough rests, prepare the cream by blending the silken tofu, cashews, half of the maple syrup, vanilla extract, and lemon juice until completely smooth and velvety.
On a lightly floured surface, roll out the dough to 1/8-inch thickness and use a round cutter to create circles.
Place several blueberries and a drop of the remaining maple syrup in the center of each circle, then fold and pinch the edges firmly to seal.
Bring a large pot of water to a gentle boil and drop the pierogi in batches, cooking until they float to the surface, plus an additional 2 minutes.
Remove with a slotted spoon and serve immediately topped with the chilled sweet cashew cream.