For the dip: In a small bowl, combine the sour cream, mayonnaise, dill, parsley, lemon juice, garlic powder, onion powder and Worcestershire. Taste and season with salt and pepper. Set aside, and garnish with more fresh dill when ready to serve.
For the pierogies: In a medium bowl, combine the flour, salt and egg. Mix until combined. Using a wooden spoon, work in the crème fraîche. As needed, add up to 2 tablespoons water to form an elastic but firm dough. Allow to rest at room temperature for 1 hour.
Scoop the warm potato flesh from the skins into a mixing bowl. (This will yield 1 to 1 ½ cups.)
Mash the potato using a fork, then stir in the farmer’s cheese, Cheddar, cooked onions and half of the green onions. Season with heavily with salt and pepper.
On a floured surface, roll out the dough to ⅛- to ¼-inch-thick. Using a 3-inch ring cutter, cut out rounds.
Place a small dollop of filling in the center, then brush the edge with water and fold over, crimping with a fork. Continue until all the pierogies are filled. (You can refrigerate or freeze the pierogies at this point for later use.)
In a medium sauté pan over medium heat, heat some butter until it begins to froth. Add half the pierogis and brown on each side, 5 to 8 minutes total. Finish with some remaining green onions in the pan. Repeat with fresh butter until the pierogis are cooked. Season with salt and pepper.
Spread the dip on the bottom of a platter, then top with the pierogies, dill and lemon juice.