Preheat the oven to 375 degrees F.
Using the butter, grease a 9-inch round pie dish.
In a medium mixing bowl, add the eggs, the sour cream, and the mayonnaise and whisk until blended.
In a small mixing bowl, add the flour, the baking powder, and the cornstarch and whisk to combine.
Add the flour mixture to the egg mixture and whisk until smooth and combined.
In a separate medium mixing bowl, add the cabbage and the salt and use your clean hands to squeeze and stir the cabbage until coated in the salt and slightly softened, about 30 seconds.
Add 2 tablespoons of the green onions and the dill to the cabbage mixture and toss lightly to combine. Step 8
Spread the cabbage mixture evenly in the bottom of the prepared pie dish.
Pour the egg mixture evenly over the cabbage mixture.
Sprinkle the top of the cabbage mixture evenly with the mozzarella.
Bake the casserole on the center rack until the top is golden, about 35 minutes.
Serve garnished with the extra green onions.