Crisp-Bottom Garlic-Parmesan Spinach Pierogi

Steps

1. Make the dough first: in a bowl mix the flour with 2 g of the salt. Add the egg, milk and one-third of the olive oil and stir into a shaggy dough, then knead 5 minutes until smooth. Cover and rest 30 minutes at room temperature.
2. While the dough rests, make the filling in a large lidded skillet: add the potato, 180 g of the water and 2 g of the salt, cover and simmer over medium heat 12–15 minutes until fork-tender and the water is nearly gone. Uncover, add the spinach and cook 1 minute until wilted.
3. Transfer the potato and spinach to a bowl and mash with two-thirds of the garlic, the mozzarella, three-quarters of the Parmesan, the black pepper and nutmeg. Cool 10 minutes. Wipe out the skillet.
4. Make the herb yogurt: stir the Greek yogurt with the remaining third of the garlic, the basil, parsley, lemon juice, lemon zest, red pepper flakes and the remaining 1 g of salt. Chill until serving.
5. Roll the dough on a floured counter to about 1/16 inch thick and cut 3-inch rounds, rerolling scraps, to get about 32. Fill each with a spoonful of filling, fold into a half-moon and pinch the edges firmly to seal.
6. Cook in two batches: heat half the remaining olive oil and half the butter in the skillet over medium-high heat, set in half the pierogi flat side down and fry 2 minutes until the bottoms are golden.
7. Pour in half of the remaining water, cover at once and steam 5–6 minutes until the dough is tender. Uncover and cook 1–2 minutes more until the water evaporates and the bottoms re-crisp. Repeat with the remaining olive oil, butter, water and pierogi.
8. Sprinkle the pierogi with the remaining Parmesan and serve with the herb yogurt.