In a mixing bowl, combine the softened butter with the chopped rosemary, thyme, sage, garlic powder, onion powder, salt, and pepper. Mix until well combined.
In a large baking dish, layer half of the sweet potato slices at the bottom. Spread half of the herb butter mixture evenly over this layer. Repeat with the remaining sweet potatoes and the rest of the herb butter.
Pour the heavy cream over the sweet potatoes, allowing it to seep through the layers. Sprinkle the grated Parmesan cheese generously on top.
Evenly sprinkle the breadcrumbs over the cheese layer.
Cover the baking dish tightly with aluminum foil and bake in the preheated oven for 30 minutes.
After 30 minutes, carefully remove the foil and bake for an additional 20-25 minutes, or until the top is golden brown and the sweet potatoes are tender when pierced with a fork.
Once baked, remove the casserole from the oven and let it cool for a few minutes. Garnish with fresh parsley before serving.