How to Make It
Preheat the oven to 350°. Line two baking sheets with parchment paper. In a small bowl, whisk the flours with the salt. In a medium bowl, using an electric mixer, beat the butter with the sugar at medium speed until light and fluffy, about 3 minutes. Beat in the egg and vanilla. At low speed, beat in the dry ingredients, pepitas and mango. Gather up the dough and knead a few times to form it into a ball.
Transfer the dough to a work surface lined with parchment paper. Using a lightly floured rolling pin, roll out the dough to a 10-by-12-inch rectangle. Transfer the dough (on the paper) to a baking sheet and freeze for 15 minutes, until firm but not frozen.
Using a sharp knife, trim the edges of the dough. Cut the dough into twenty 2-by-3-inch rectangles, then cut each in half to form 40 triangles. Arrange the cookies on the prepared baking sheets, spacing them 1 inch apart. Bake for 10 to 12 minutes, until lightly golden and set. Transfer the cookies to racks to cool.