How to Make It
Preheat the oven to 450°. In a large ovenproof skillet, melt 2 tablespoons of the butter over high heat. Season the squab with salt and pepper. When the butter is very hot, add the squab, breast side down, and brown well on all sides, about 9 minutes. Turn breast side up and roast in the upper third of the oven, basting a few times, for about 15 minutes, or until the breast meat is medium rare. Transfer the squab to a warm plate.
Pour off the fat in the skillet. Add the Madeira and simmer over moderate heat for 2 minutes, scraping the bottom of the pan with a wooden spoon to loosen any browned bits. Remove from the heat.
Using a boning knife, cut along the breast bone and around the legs to halve and partially bone each squab. Arrange 2 halves on each plate. Pour the carving juices into the pan sauce and simmer for 1 minute over moderately high heat. Remove from the heat and swirl in the remaining 1 tablespoon chilled butter. Season the sauce with salt and pepper and pour over the squab. Scatter the rose petals on top and serve.