In a medium bowl, mix together the flour, salt, baking soda, and cornstarch until well-combined. Set aside.

In a mixer, add the granulated sugar, brown sugar, instant espresso, and unsalted butter. Beat until light and fluffy – about 5 minutes.

Beat in the eggs and vanilla and beat until it is well combined and fluffy – about another 2 – 3 minutes.

Stir in the four and mix until just combined and there are no streaks of flour. Fold in the chocolate chips until they are evenly dispersed.

Cover the bowl with plastic wrap and chill in the refrigerator for about an hour.

Preheat the oven to 350°F. Line two baking sheets with parchment paper.

Portion out balls of dough that are about 2 tablespoons big and place on the baking sheets at least an inch and a half apart.

Bake each baking sheet one at a time for 8 – 10 minutes, or until the edges are a golden brown and the middles are puffy and just set. They will look slightly underdone, and that is okay. Remove from the oven and leave on the baking sheet for another minute.

Transfer the cookies to a wire rack and allow to cool to room temperature before serving.