Step 1

Preheat the oven to 375°F.

Step 2

Melt 1 tablespoon of the butter in a large skillet over medium heat. Add the zucchini slices and season with 1/2 teaspoon kosher salt and the black pepper. Cook, stirring occasionally, until the zucchini is softened but still vibrant and green, about 10 minutes. Remove from the heat.

Step 3

While the zucchini is cooking, melt 2 tablespoons of the butter in the microwave or on the stove top, and set aside to cool. In a medium bowl, mix 1 tablespoon of the cooled, melted butter with the sour cream, 1/2 teaspoon kosher salt, and then the egg yolk. Fold into the zucchini mixture with 1/4 cup of the grated Parmesan cheese and 1 tablespoon of the chives.

Step 4

Spray a 7 X 11-inch or 2-quart baking dish with cooking spray, then transfer the zucchini mixture to the dish. In a small bowl, combine the bread crumbs with the remaining melted butter and Parmesan cheese, plus the remaining chopped chives. Sprinkle the bread crumb mixture evenly over the zucchini. Cover with foil and bake until warmed through and the cheese has started to melt, about 15-20 minutes. Remove the foil and raise the oven temperature to 450°F. Bake until the top is browned and the filling is bubbling at the edges, about 10 minutes. Sprinkle with more fresh chives if desired, and serve.