- 1 cup (2 sticks) unsalted butter, room temperature
- 1/2 cup powdered sugar
- 1 teaspoon freshly ground black pepper
- 3/4 teaspoon kosher salt
- 2 cups all-purpose flour plus more
- 1 cup finely grated Parmesan (about 2 ounces)
- 1 tablespoon fennel seeds
- 1 teaspoon Maldon sea salt or other coarse salt
- 2 tablespoons extra-virgin olive oil
- Using an electric mixer, beat butter in a medium bowl on low speed until smooth, 1-2 minutes. Add powdered sugar, pepper, and kosher salt. Reduce speed to medium and beat, occasionally scraping down sides of bowl, until light and fluffy, 4-5 minutes. Add flour and cheese. Reduce mixer speed to low and beat mixture just until dough comes together.
- Wrap dough in plastic and flatten into a rectangle. Chill until firm, at least 2 hours. DO AHEAD: Dough can be made 5 days ahead. Keep chilled. Let stand at room temperature for 30 minutes before continuing.
- Place fennel seeds in a resealable plastic freezer bag. Coarsely crush with a rolling pin or the bottom of a skillet. Alternatively, pulse in a spice mill until coarsely crushed. Transfer to a small bowl; stir in sea salt. Set fennel salt aside.
- Arrange a rack in center of oven and preheat to 350°F. Line a baking sheet with parchment paper. Remove plastic wrap from dough. Roll out dough on a lightly floured surface to a 10×8″ rectangle about 1/4″ thick. Cut in thirds crosswise, then cut each third crosswise into 6 rectangles. Arrange cookies on prepared baking sheet, spacing 1″ apart. Brush cookies generously with oil, then sprinkle with fennel salt.
- Bake, rotating sheet halfway through, until cookies are golden brown (flecks of cheese will be slightly darker), 20-24 minutes. Let cool on sheets for at least 10 minutes. Serve warm or at room temperature. DO AHEAD: Can be made 2 days ahead. Store airtight at room temperature.