- 1/2 cup unsalted butter, at room temperature
- 1/2 cup powdered sugar
- 2-inch length vanilla bean, split and seeds scraped out
- 1 egg yolk
- 1 1/4 cups all-purpose flour
- 1/4 teaspoon salt
- 1/2 cup coarsely grated bittersweet chocolate (about 1 1/4 ounces) (see note)
In the bowl of a stand mixer, beat butter on medium speed until pale and fluffy, about 1 minute. Scrape down the sides of the bowl, add powdered sugar and vanilla seeds, and beat (starting slowly at the lowest speed so sugar won’t puff out of the bowl) at medium speed for 2 minutes. Add egg yolk and beat for 1 minute. Sprinkle in flour and salt and blend at low speed just until no white streaks of flour remain. Gently fold in chocolate.
Press dough into a cylinder about 2-inches in diameter. Wrap in plastic wrap and refrigerate for at least 2 hours, or for as long as 3 days.
Preheat oven to 350° F. Line two baking sheets with parchment paper.
Slice chilled dough into disks 1/4-inch-thick. Place disks on the prepared baking sheets about 1-inch apart. Bake for 15 to 18 minutes, until edges are light golden brown. They will get crunchier as they cool. Once completely cool, store in an air-tight container at room temperature for up to 1 week.
The largest holes of a box grater are the perfect size for grating chocolate; we suggest looking for a bar that’s in the 70 percent cacao range.