Directions

1. Preheat oven to 425 degrees. In a small bowl, sift together flour, cornstarch, and salt; set aside. Line three baking sheets with parchment paper; set aside.
2. In the bowl of an electric mixer fitted with the whisk attachment, beat egg yolks, 1/4 cup granulated sugar, and the vanilla until light and creamy, about 4 minutes; set aside.
3. In the clean bowl of an electric mixer fitted with a clean whisk attachment, beat egg whites on medium-high speed with 1/4 cup granulated sugar until foamy. Add cream of tartar, and continue to beat until soft peaks form. With machine running, gradually add remaining 1/4 cup granulated sugar, beating into stiff, glossy peaks.
4. Fold egg-yolk mixture into egg-white mixture, then fold in dry ingredients. Do not overmix.
5. Transfer to a pastry bag fitted with a 1/2-inch round tip. Pipe 4-inch cookies onto prepared baking sheets leaving about 1 inch between cookies. Lightly dust with confectioners' sugar. Bake until just beginning to brown around the edges, about 8 minutes; rotate pans once after 4 minutes. Transfer to wire racks to cool. Will keep, at room temperature, in an airtight container for up to 2 weeks.
6. Just before serving, dust with confectioners' sugar and, if desired, sandwich raspberry jam or lemon curd between them.