Preheat your oven to 375°F (190°C) and grease a 13 x 9-inch baking dish with olive oil.

Arrange 12 pierogi in a single layer at the bottom of the greased baking dish.

In a mixing bowl, combine the cheddar cheese soup with three quarters of the shredded cheddar cheese and pour half over the arranged pierogi.

Add half of the farmer’s cheese, drained spinach, chopped onion, and diced smoked kielbasa, sprinkling with kosher salt.

Repeat the layering with remaining pierogi, cheese soup mixture, farmer’s cheese, spinach, onion, and kielbasa.

Sprinkle remaining shredded cheddar cheese on top and drizzle a little olive oil over it.

Bake in the preheated oven for 45 minutes or until cheese is bubbly and edges are lightly golden.

Remove from the oven, let cool for a few minutes, and garnish with minced scallions before serving.