Preheat oven to 350°F (177°C). Line a large cookie sheet with parchment paper.
In a large microwave-safe mixing bowl, add chocolate chips and butter. Heat in microwave in 15-20 second intervals, stirring in between with a spatula, until you have a smooth melted chocolate batter. You can also melt the chocolate and butter on the stove using the double boiler method.
Stir in the cornstarch until it is completely and evenly incorporated into the batter and no streaks of cornstarch remain. Adding the cornstarch should also thicken the mixture.
Using a 2 tsp cookie scoop, scoop cookie mixture and release onto prepared cookie sheet, spaced 1 inch apart. The batter should be thick enough that it won't spread out on its own. Very gently smooh just the surface of the cookies (be careful not to flatten the cookies) either with the back of a metal spoon or your fingers. If the batter is sticking to you, you can slightly dampen your fingers or the spoon before smoothing.
Bake cookies for about 6 minutes or until the batter looks dry and the cookies have small cracks on the surface. Let cookies cool and set on the cookie sheet before removing them with a cookie spatula. If desired, you can dust the tops with powdered sugar before serving.
Notes
Make sure to use semisweet chocolate chips. The cookies will not set with milk or white chocolate.
If you like salt flavor in your cookies make sure to use salted butter.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.