Pretzel Shortbread Cookies

Bahan-bahan (16 porsi)

• 1 large handful (about 12) thin hard pretzels
• 8 ounces unsalted butter, softened and cut into chunks
• 1 cup powdered sugar
• 1 1/2 cups all purpose flour, plus more for sprinkling
• 1/4 cup food-grade lye (see note)
• Pretzel salt, to top