Preheat the oven to 375 degrees F. Generously grease a shallow 9×13-inch casserole dish or similar 3-quart baking dish with non-stick cooking spray.

Heat 1 tablespoon of the olive oil in a large skillet or Dutch oven over medium heat. Add half of the butternut squash, ½ tablespoon of thyme, ¼ teaspoon salt, and 1/8 teaspoon pepper. Sauté until the squash is beginning to brown, about 3 minutes.

Add half of the kale, half of the onions, and half of the garlic. Cook until the kale and onions begin to soften, about 4 minutes.

Add ½ cup of the chicken stock, stir, and let cook for 1 minute to reduce slightly. Transfer the mixture to the prepared baking dish, spreading it into a relatively even layer.

Heat the remaining tablespoon of olive oil in the skillet. Repeat the previous steps with the remaining half of each ingredient. Transfer the rest of the filling to the casserole dish. Cover with aluminum foil and bake for 30 to 35 minutes or until the squash is soft when pierced with a knife.

While the casserole bakes, prepare the topping: In a small bowl, combine the breadcrumbs, Parmesan, sage, nutmeg, and salt. Pour the melted butter over the top and stir to combine.

Remove the casserole from the oven, uncover, and sprinkle the breadcrumb mixture evenly on top.

Reduce the oven temperature to 350 degrees F and return the dish to the oven. Bake uncovered until the breadcrumbs are golden, about 20 minutes. Serve warm.