Mix together flour, cornstarch, and a pinch of salt. Separately whisk lightly sugar and oil and start to knead the flours with this mixture.
Dissolve the ammonia into warm milk and add it gradually to the cookie dough (if you use baking powder instead, add it to the flours at the beginning). Once you obtain a smooth and sticky dough, add the dried fruit mix and knead a little more to distribute evenly.
Form cookie dough into balls and roll them in the cornflakes; place the cookies on a baking sheet.
Bake in a preheated oven at 360°F for 20 minutes. Let the cookies cool down in the oven with the door slightly opened, so that they can dry out well.