Gluten-Free Chocolate Crinkle Cookies

I really love Chocolate Crinkle Cookies, and I often buy a few from the local bakery when I'm out and about. Sometimes I make them. I've posted several Chocolate Crinkle Cookies in the past, including a very similar one to this one. But at that time, I didn't mention that these cookies are Gluten-Free, so here's an updated recipe for Gluten-Free Chocolate Crinkle Cookies. These cookies can be very fudgy, almost runny, so mind the tip at the end of the recipe. I've made a few adaptations.

GLUTEN-FREE CHOCOLATE CRINKLE COOKIES

Ingredients: 
1-1/2 cups dark chocolate (70-75% cacao), chopped
3 large egg whites, room temperature
1 3/4 cups powdered sugar, divided
1/2 cup unsweetened DARK cocoa powder
1 Tbsp cornstarch
1/4 teaspoon salt

Directions
Preheat oven to 350 degrees F.
Line two baking sheets with parchment paper; set aside.
Melt 1 cup chopped chocolate over double broiler, or metal bowl over saucepan of simmering water. Set aside to cool slightly.
In large bowl, with electric hand mixer, beat egg whites until frothy and soft peaks form. Gradually beat in 1/2 cup powdered sugar, and continue beating until mixture looks like soft marshmallow creme.
In another bowl, whisk together 1 cup powdered sugar, cocoa powder, cornstarch and salt.
Slowly add dry ingredients to the egg white mixture, mixing on low speed until combined. Stir in melted chocolate and 1/2 cup chocolate chips.
If batter is stiff, proceed to the next step. If not, allow to sit until it has thickened enough to roll into balls.
Place remaining 1/2 cup powdered sugar in a bowl.
Roll rounded tablespoons of dough into balls; then roll in powdered sugar to coat.
Place on prepared baking sheets, about 2 inches apart.
Bake for 10 minutes, or until puffed and tops are cracked.
Cool on baking sheets for 5 minutes, then transfer to a wire rack to cool completely.

*Note: Be sure to let the dough thicken. The thicker the dough, the thicker the cookies.