How to Make It
Heat oven to 400° F. Heat the oil in a large skillet over medium-high heat. Add the sausage and cook, tossing occasionally, until browned, 4 to 6 minutes. Using a slotted spoon, transfer the sausage to a large bowl.
Add the onions, rosemary, ¼ teaspoon salt, and ¼ teaspoon pepper to the drippings in the skillet and cook, stirring, until softened, 3 to 5 minutes. Sprinkle with the flour and cook, stirring, for 1 minute. Add the broth and simmer until thickened, 2 to 3 minutes. Add the kale, vinegar, ½ teaspoon salt, and ¼ teaspoon pepper and cook, tossing, until the kale is wilted, 2 to 3 minutes.
Add the kale mixture and cauliflower to the sausage and toss to combine. Transfer to a 9-by-13-inch or some other 3-quart baking dish and top with the puff pastry, overlapping the rectangles slightly.
Bake until the pastry is golden and the filling is bubbling, 25 to 30 minutes. Let cool for 5 minutes before serving.