Combine the cauliflower and one tablespoon salt in a large saucepan and cover with water.

Bring to a boil over medium-high heat. Reduce heat to medium and cook until cauliflower is tender, about 15–20 minutes.

Drain cauliflower, then add cheese, butter, one teaspoon salt, and pepper. Mash until smooth and all ingredients are completely combined. Transfer the mixture to a bowl and cool completely.

Combine all dough ingredients in a large mixing bowl fitted with a dough hook. Mix on medium speed for eight minutes until the dough is smooth and elastic. (Dough can be covered and refrigerated until ready to assemble.)

Line two baking sheets with Gefen Parchment Paper.

On a lightly floured surface, roll dough to about one-eighth of an inch. Use a three-inch (seven- and- a- half-centimeter) round cookie cutter add (the top of a glass works fine too) to cut as many circles as fit.

Place one tablespoon of cauliflower-cheese filling in the center of each dough circle. Fold the dough over to form a half-circle shape. Pinch the ends to seal closed. The dough may shrink after being shaped into a circle. Simply stretch and reshape the dough and fill.

Gather the dough scraps, form into a ball, and repeat the above steps until you have used up all the dough and filling.

Fold over immediately and seal. Transfer to the prepared baking sheet.

Melt the butter in a large frying pan over medium-low heat. Add onion and salt and cook until the onions are caramelized, about 15–20 minutes. Set aside.

Bring a large pot of water to a boil. Add one tablespoon salt to the water. Place six to 10 pierogis in the boiling water and cook for about five minutes, until they’re tender and float to the top.

Using a slotted spoon, transfer the pierogis to the frying pan with the caramelized onions. Return water to a boil and repeat until all the pierogis are cooked and transferred to the frying pan.

Return the frying pan to the heat. Add two tablespoons of cooking water to the pan.

Raise the heat and stir for two minutes, then transfer the pierogis to a serving plate.