Preheat the oven to 350°F. Line a rimmed 18 × 13-inch baking sheet with a Silpat. Sift half of the powder over the baking sheet in an even layer. Bake for 3 minutes, or until the sugar is melted. Remove from the oven, cover with a sheet of parchment paper, and carefully flip the Silpat onto a flat surface. Peel off the Silpat, and with the aid of a ruler, cut the sugar into 4 triangles that are 3½ inches long and have a base of ¾ inch. Lift the triangles with an offset spatula and transfer to a flat tray. If the sugar becomes too brittle when cut or lifted, slide the parchment back onto the baking sheet and place in the oven for 30 seconds to soften. Cool the tuiles at room temperature and store in an airtight container.