1. Preheat oven to 400 degrees. On a lightly floured work surface, roll out puff pastry to a 12-inch square; transfer to a parchment-lined baking sheet. With a paring knife, lightly score pastry 1/2 inch from edges, creating a border. Toss together broccoli, oil, garlic, and red-pepper flakes; season with salt and pepper. Scatter broccoli mixture evenly on pastry and sprinkle with Pecorino. Bake until pastry is deep golden and puffed, about 30 minutes. Let cool slightly before cutting into squares. Serve warm or at room temperature.