Lemon-Pistachio Wreaths

INGREDIENTS

• 1 teaspoon baking powder
• 1/4 teaspoon salt
• 1 cup all-purpose flour, plus more for work surface
• 3/4 cup plus 1 tablespoon cornstarch
• 1/2 cup (1 stick) unsalted butter, softened
• 1/2 cup plus 1 tablespoon granulated sugar
• 2 large egg yolks, room temperature
• 5 teaspoons finely grated lemon zest, plus 2 tablespoons fresh lemon juice
• 1 teaspoon pure vanilla extract
• 1 3/4 cups confectioners’ sugar
• 1 1/2 cups shelled unsalted pistachios, toasted and coarsely chopped