Dumpling casserole

Ingredients:

Dough for dumplings

• 1 large egg
• 8 tbsp unsalted butter, softened, plus extra for greasing the pan
• 3/4 cup sour cream + extra for serving
• 1 tbsp chopped fresh chives, plus extra for serving (optional)
• 1 teaspoon coarse salt
• 2 cups premium flour + extra for work

Filling

• 900 g Russet-Burbank potatoes, peeled and cut into large chunks
• 1 cup heavy cream, hot
• 8 tbsp chilled butter, diced
• 1 tbsp. l. olive oil
• 450 g bacon, chopped
• 2 large onions, thinly sliced
• 1.5 cups grated Gruyere
• 1.5 cups grated farmer's cheese

Preparation:

1. Dough for dumplings:

   
   In a bowl, mix the egg, butter, sour cream, green onions, and salt by hand. Don't worry if the mixture isn't smooth; don't overmix. Add the flour and knead the dough with your hands. Wrap the dough in plastic wrap and refrigerate for at least 2 hours and up to 24 hours.
   

2. Filling:

   
   Place the potatoes in a large saucepan and cover with cold water to a depth of 2 inches. Bring to a boil. Season generously with salt. Reduce heat to maintain a gentle simmer and cook until the potatoes are tender when pierced with a knife. Drain and return the potatoes to the saucepan. Mash them, gradually adding hot cream and cold butter. Season with salt and pepper to taste and set aside.
   
3. Heat olive oil in a large skillet over medium-high heat. Cook the bacon, stirring occasionally, until crisp, about 10 minutes. Transfer the bacon to a plate with a slotted spoon. Reduce the heat to medium, add the onion, and stir to coat with the rendered bacon fat. Season with salt and pepper. Cook, stirring frequently, until the onion is caramelized. Let cool.
4. Preheat oven to 175°C. Grease a 22x32 cm baking dish or frying pan with butter.
5. On a lightly floured work surface, roll the vareniki dough out with a rolling pin into a 0.3 cm thick rectangle. Cut into 10 x 32 cm strips, re-rolling any scraps if necessary. You'll need 14-20 strips.

6. Assembly:

   
   Arrange the mashed potatoes, crispy bacon, caramelized onions, dough strips, and cheeses on a table nearby. Place a single layer of pierogi dough strips in the bottom of a greased pan, overlapping them slightly. Top the dough with a 1/2-inch-thick layer of mashed potatoes. Top with some caramelized onions, bacon, and a sprinkling of grated Gruyere and farmer's cheese. Repeat the layering to use up all the remaining ingredients, finishing with the dough and then sprinkling with a little Gruyere and farmer's cheese. Season with freshly ground black pepper.
   
7. Bake until the casserole is bubbly and the cheese on top is golden, about 40 minutes. Let rest for 15-20 minutes and serve with a dollop of sour cream and a sprinkle of chives, if using.