Preheat oven to 375 degrees.
In the bowl of a stand mixer, or in a large bowl with a spatula, mix the butter and sugar until well-blended.
Add the vanilla extract, mix, then add the cornstarch-water mix, flour, powdered hazelnuts, cacao powder, and baking powder. Mix until combined, and then stir in the chocolate chips.
On a cookie sheet lined with parchment paper, drop ¾-inch balls of dough at least an inch apart(don't worry too much about shaping them, just dropping them with a rounded spoon is fine, or use your fingers. The cookies will spread as they bake.)
Place the cookie sheet in the oven and bake for 10 minutes. Let the cookies cool on the sheet for a couple of minutes, then, using a thin spatula, remove to a rack to cool.