Gather ingredients and prep the oven and pan. Preheat the oven to 350°F and grease a 1 1/2-quart baking dish.

Prep the spinach and make the filling. Thaw the spinach in a colander under cool running water and squeeze it vigorously to remove as much excess moisture as possible. Combine the drained spinach with the softened cream cheese and half of the melted butter in a bowl. Taste and season with salt and pepper, as needed. Spread the spinach and cream cheese mixture in the prepared baking dish. 

Finish with breadcrumb topping. Combine the remaining melted butter with the seasoned breadcrumbs and Parmesan cheese; sprinkle over the casserole.

Bake. Bake 25 minutes or until the topping is lightly browned and the spinach mixture is bubbling around the edges.