Preheat the oven to 450°.
In a large roasting pan, toss the kale, potatoes and onion with the olive oil and hot smoked paprika. Season with salt (optional) and pepper and spread in an even layer.
Place chicken, if using, over veggies.
Cover the pan with foil. Roast in the upper third of the oven for 20 minutes. Remove the foil and roast for 20 minutes longer, until the chicken (if using) is cooked through and the potatoes are tender. At this point, everything should be cooked through with some caramelization on the potatoes and onions and with the kale crispy around the edges.
We made this recipe with chicken the first couple of times and then realized that we didn’t particularly care about the chicken and it then became a vegetarian favorite! It is good as a leftover, but the kale, of course, will no longer be crispy.