Measure out all ingredients and ensure your butter is softened to room temperature—this is crucial for proper creaming and incorporation of air into the dough. In a medium bowl, whisk together the flour, baking soda, sea salt, cornstarch, and instant espresso powder. The espresso powder won't make the cookies taste like coffee; instead, it deepens and enhances the chocolate flavor. Set this dry mixture aside.

In a large mixing bowl, beat the softened butter with the granulated sugar and brown sugar for about 5 minutes on medium speed until the mixture is light, fluffy, and pale in color. This creaming process incorporates air into the dough, which helps the cookies rise and develop a tender crumb. Scrape down the bowl occasionally to ensure everything is evenly combined.

Add the vanilla extract and room-temperature eggs one at a time to the creamed butter mixture, beating well after each addition. Room temperature eggs incorporate more smoothly into the dough and help create a cohesive batter. Continue beating until the mixture is well combined and slightly fluffy, about 1-2 minutes total.

Gently fold the dry ingredient mixture from Step 1 into the wet ingredients using a spatula or wooden spoon, stirring until just combined. Avoid overmixing, as this can develop too much gluten and result in tougher cookies. The dough should come together with no visible streaks of flour.

Fold the semi-sweet chocolate chips into the dough until evenly distributed. I like to reserve a small handful of chips to press onto the top of each cookie before baking—they'll add visual appeal and extra chocolate in every bite. Cover the dough and refrigerate for at least 1 hour; this allows the dough to firm up and helps prevent the cookies from spreading too much during baking.

While the dough chills, preheat your oven to 375°F. Once the dough has chilled and the oven is ready, use a cookie scoop or spoon to portion dough onto parchment-lined baking sheets, spacing them about 2 inches apart to allow for spreading. If you reserved chocolate chips, press a few onto the top of each dough ball now.

Bake the cookies for 10-12 minutes until the edges are golden brown but the centers still look slightly underbaked—they'll continue to cook on the hot pan after removal from the oven. Let the cookies cool on the baking sheet for 5 minutes to set, then transfer them to a wire rack to cool completely. I find this method gives you cookies with crispy edges and chewy centers, the perfect texture contrast.