1/2 cup pecan pieces
8 tablespoons (1 stick) unsalted butter, at room temperature
1/2 cup freshly grated Parmesan cheese
1 cup flour
1 tablespoon minced thyme leaves
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
Preheat the oven to 375 degrees.
Spread the pecan pieces on a baking sheet and toast in the oven for about 8 minutes, until they are fragrant. Transfer to a cutting board to cool, then coarsely chop.
Place the butter in the bowl of a stand or hand-held electric mixer; beat on medium speed for several minutes, until fluffy and light. Add the Parmesan cheese and beat until well blended.
Remove the bowl from the mixer, then add the flour, toasted pecans, thyme, salt and pepper. Stir with a wooden spoon or spatula, then use your hands to help the dough come together. Divide the dough in half, then shape each half into a log 1 1/2 to 2 inches wide. Wrap the logs in plastic wrap and refrigerate for at least 1 hour or up to 3 days.
When ready to bake, preheat the oven to 350 degrees. Line a baking sheet with parchment paper.
Cut one of the logs crosswise into 1/4-inch slices, arranging the rounds of dough 1 inch apart on the baking sheet. Bake for about 20 minutes, until golden. Transfer the shortbread to wire racks to cool completely before storing. Repeat to use all of the dough.