In a food processor, pulse together flours with salt.
Add in butter and pulse a few times until cut into pea sized pieces.
Add remaining ingredients and continue to pulse until dough comes together into a ball, about 2 minutes.
Transfer dough onto a floured surface and knead into a smooth ball. If dough feels sticky, knead in a little more flour.Divide into 2 flattened rounds and wrap in plastic wrap and place in fridge for at least 30 minutes to rest. Dough can stay like this for up to 2 days. Dough also freezes well, let thaw in fridge.
To Fill Pierogies: Working on round at a time, roll out dough to 1/2 inch thick on lightly floured surface. Punch out circles with cookie cutter and fill with rounded tsp of desired filling. Resist overfilling! With fingers wrap dough around filling and pinch to seal edges. Dough should self seal but you can use a dab of water if necessary. You can also crimp with back of a fork.
Re-roll scraps, just knead them up and pop back in fridge to chill another 10 minutes before re-rolling.
To Cook Pierogies: Cook in boiling salted water until they float to the top, then strain and saute in butter.