Grease a 2-3 quart casserole dish. Set aside.
Heat a very large skillet (the largest you have!) over medium-high heat. Add all of the Kale (2 bunch) to the skillet and add 1 cup of water. Cover the skillet and cook for 10-15 minutes, stirring occasionally until the kale is wilted.
Once the kale is wilted and all of the water has been absorbed, remove the kale from the skillet and set aside.
Return the skillet to medium heat and add Olive Oil (2 tablespoon). When the skillet is hot, sprinkle in the Cremini Mushroom (1 pound) in a single layer. Don't stir them! Let them sizzle until they have caramelized on the bottom, about 2 minutes.
When the bottoms are caramelized, toss them once and season with Salt (to taste) and Ground Black Pepper (to taste) to taste. Continue to cook without stirring for about 5 minutes.
Now add the Butter (1 tablespoon) to the skillet and cook until the butter begins to brown. Once the butter is browned reduce the heat and add the Garlic (2 clove), Fresh Thyme (2 tablespoon), and Ground Nutmeg (1/4 teaspoon) and cook for about 10 seconds.
Now add the kale back to the skillet with the mushrooms, garlic, and spices and toss well.
Sprinkle the All-Purpose Flour (4 tablespoon) over the kale and mushrooms and cook for 1 minute.
Add the Milk (1 cup) and Chicken Broth (1 cup), bring to a boil and cook 2-3 minutes or until there is a thick sauce. Add the Heavy Cream (1/4 cup) and stir to combine.
Remove from the heat and stir in the Wild Rice (4 cup). Pour the mixture into the prepared casserole dish.
Preheat the oven to 375 degrees F (190 degrees C).
Now wipe the skillet and add the Olive Oil (2 tablespoon) and cook over medium-high heat.
Add the Sweet Onion (2) and 1/4 teaspoon each salt and pepper. Cook, stirring constantly, until the onions begin to soften, about 5 minutes. Continue to cook until the onions are golden brown, about 20 minutes.
Sprinkle half the Gruyère Cheese (1 1/2 cup) over the casserole and then add the onions and the remaining cheese.
Bake the casserole for 20-25 minutes or until the cheese is melted and the onions are crispy. Serve!