Preheat the oven to 325°F. Lightly grease a 2-quart baking dish with butter. Bring a pot of salted water to a boil over high heat. Add the cauliflower and blanch until tender, about 5 minutes. Drain the cauliflower and transfer immediately to a food processor. Add the 4 tablespoons butter, season with salt and pepper, and puree until smooth. Pour the cauliflower puree into a large mixing bowl and whisk in the ricotta, egg yolks, Parmesan cheese, 1 teaspoon salt, and ½ teaspoon pepper. Transfer to the prepared baking dish and bake until the pudding is golden brown and nearly firm in the center, about 50 minutes. Serve warm.