Baked Deruny Casserole with Mushrooms

Prepare the Deruny

1. 1Squeeze excess moisture from the grated potatoes using a clean kitchen towel or cheesecloth.
2. 2In a large bowl, combine the squeezed potatoes, chopped onion, eggs, flour, salt, and pepper. Mix well until everything is just combined.
3. 3Heat vegetable oil in a large skillet over medium-high heat. Drop spoonfuls of the potato mixture into the hot oil and flatten them slightly to form small pancakes (deruny).
4. 4Fry the deruny for about 3-4 minutes per side, until golden brown and cooked through. Adjust heat as needed to prevent burning. Drain on paper towels and set aside.

Prepare the Filling

1. 1In the same skillet (or a clean one), melt the butter over medium heat. Add the sliced onions and cook until softened and translucent, about 5-7 minutes.
2. 2Add the sliced mushrooms and minced garlic to the skillet. Cook, stirring occasionally, until the mushrooms are browned and tender, about 8-10 minutes. Season with salt and pepper.
3. 3In a bowl, whisk together the sour cream and half of the grated cheese. Season with salt and pepper if desired.

Assemble and Bake

1. 1Preheat your oven to 190°C (375°F).
2. 2Lightly grease a 9x13 inch baking dish.
3. 3Arrange half of the fried deruny in a single layer in the prepared baking dish.
4. 4Spoon the mushroom and onion mixture evenly over the deruny layer.
5. 5Pour the sour cream and cheese mixture over the mushroom layer.
6. 6Top with the remaining deruny, pressing down gently.
7. 7Sprinkle the remaining grated cheese over the top.
8. 8Bake for 25-30 minutes, or until the casserole is bubbly and the cheese is golden brown and melted.
9. 9Let it rest for a few minutes before serving. Garnish with fresh dill if desired.