In a large pot, bring the cream to a gentle boil over medium-high heat. Boil until the cream is reduced to 1 ½ cups, about 5 minutes. Add the garlic, chile flakes, nutmeg, ½ cup of the onion, 1 teaspoon salt, and ½teaspoon pepper and stir well. Return to a boil, then reduce the heat to medium and simmer, stirring occasionally, for 15 minutes.
Meanwhile, heat the oil in a large skillet over medium-high heat. Add the remaining ½ cup onion and ½ teaspoon salt. Cook, stirring often, until onion begins to soften, about 2 minutes. Add the kale, a handful at a time, stirring to wilt after each addition. Cover and cook, stirring occasionally, until tender, about 10 minutes.
Remove the cover. Using tongs, remove the kale in batches to the pot with the cream, while squeezing out as much excess water as possible. Stir the cream mixture well. Season to taste with salt and pepper, and serve hot.