In a medium bowl, combine egg, sugar, oil, and vanilla until smooth.
In a large bowl, combine flour, oreos, cornstarch, baking powder and salt. Pour wet into dry ingredients.
Mix until a dough forms.
Flatten into a disc, and wrap in plastic wrap. Refrigerate for at least 45 minutes.
Preheat the oven to 350F. Line 2 trays with baking paper.
Roll dough out on a floured surface to 1/8th inch thickness (if they are too thick, the dough will crack when shaping.
Using a 3-inch circular cookie cutter, cut out circles, setting them aside. Repeat with remaining dough.
Use a pastry brush to brush the egg on the dough.
Place ½ tsp crushed oreos and 1 tsp white chocolate chips in the center of each circle.
Fold the dough into a triangle, pinching the corners tightly.
Brush with egg wash.
Bake for 12-14 minutes or until golden.
Transfer to a cooling rack.
Enjoy!