We use two kinds of kale in this holiday-style dressing, but you could also use two bunches of a single type. Stir in one cup chopped raw cashews before baking the dressing if you like.
Place 1 cup of the millet in a medium saucepan over medium-high heat. Cook, shaking the pan, until grains are lightly toasted, about 2 minutes. Pour in 2 3/4 cups of the broth and bring to a boil. Lower the heat, cover and simmer until millet is tender and most of broth is absorbed, about 30 minutes. Remove from the heat and let sit, covered, for at least 5 minutes.
Meanwhile, combine kale, onions and 1/2 cup water in a large pot over medium heat. Cover and cook, stirring frequently, until kale is very tender, 12 to 15 minutes. Stir in cranberries, 1/2 teaspoon of the salt and pepper. In a small saucepan, bring remaining 1 cup broth to a boil. In a small cup, whisk together cornstarch and 1 tablespoon water; stir mixture into broth. Cook, stirring, until thickened, about 2 minutes.
Preheat the oven to 375°F. Fold millet into the pot with kale. Stir in cornstarch mixture. Scoop dressing into a 2-quart baking dish. Bake until browned on top and heated through, about 35 minutes. Cool for 15 minutes before serving.
Meanwhile, place remaining 3 tablespoons millet in a large, heavy skillet over medium heat. Cook, shaking the pan frequently, until grains are lightly browned and some have popped, about 4 minutes. Immediately remove from the heat, stir in remaining pinch salt and sprinkle over baked dressing.