Other greens work well here, too: spinach, mustard greens, Swiss chard, collards, beet greens, and turnip greens each contribute their distinctive flavor, all with slightly different results.
Preheat oven to 425 F. Heat oil in a large skillet over medium high. Add kale and cook, tossing frequently, until wilted, about 5 minutes. Transfer to plate and let cool.2.
Mix ricotta with kale in a shallow baking dish, and season with salt and pepper. Bake until golden brown on top and bubbling, about 12 minutes. Let cool slightly before serving, with crackers.