Start by crushing Oreo cookies - put them in a plastic zip bag and crush with rolling pin, or some other solid object. 

Next, combine dry ingredients (flour, powdered sugar, cornstarch, salt, baking powder) in a medium dish.

Meanwhile, in a separate dish, mix wet ingredients - mix cream cheese and butter first, until it´s smooth, then add egg and vanilla and beat until it´s combined.

Next, add dry ingredients and beat until it´s combined and fold in crushed Oreos.  The dough will be very soft and sticky. Cover it with a plastic foliage and chill in the fridge for 45 min-1h.

Meanwhile, prepare baking sheet and line it with a parchment paper, them preheat the oven to 375 F.  Take the dough out of the fridge and spoon cookies into already prepared baking sheet 1.5 inches apart. You can correct the shape of cookies with your hand, if necessary.

If you want more intense flavor, put some crushed Oreo cookies on top and bake for 10 minutes.