Step 1

Place the softened butter and sugar in a large bowl (or the bowl of a stand mixer). With a hand mixer (or stand mixer with a paddle attachment) on medium-high speed, beat until very light and fluffy, 3-4 minutes. Add the egg and vanilla and mix well to combine. Add the flour 1 cup at a time, mixing on low to combine completely in between each addition. Scrape the bottom and sides of the bowl as needed.

Step 2

Transfer the dough to a piping bag fitted with a large, star tip (with a wide opening). Pipe the dough in a circle shape, about 2" in diameter, overlapping by about 1/2-inch at the edges. Sprinkle all over with sparkling sugar. Refrigerate the cookies for 30 minutes (or freeze for 15 minutes) in order to firm up and prevent spreading while baking.

Step 3

Preheat the oven to 350 degrees. Bake cookies for 12-15 minutes, until the edges are just lightly golden. Let cool on a sheet tray for 5 minutes, then carefully transfer to a cooling rack to cool completely. Once cool, store in an air-tight container in a single layer, between layers of parchment paper, at room temperature for up to 1 week.