Preheat your oven to 350°F (177°C) and line several baking sheets with parchment paper.
In an electric stand mixer fitted with the paddle attachment, cream your brown sugar, granulated sugar, butter, oil, vanilla and espresso powder on medium speed for about 4 to 5 minutes or until light in color and texture. Add the eggs, baking powder, baking soda and salt and mix on medium until everything is well blended, about 1 minute more. Take the bowl out of the mixer.
Add the flour and mix until barely blended and you still see streaks of flour. Be sure to scrape the sides and bottom of the bowl to make sure everything is well combined. Add the chocolate and mix until evenly distributed throughout. Place 2-tablespoon size dough balls on the prepared baking sheet leaving 2 inches (5 cm) of space between the dough balls.
Bake one sheet at a time in the center of the oven for about 11 to 12 minutes. They will look slightly underbaked. Allow the cookies to cool on the baking sheet for 10 minutes, and then move to a rack to finish cooling. Sprinkle with sea salt flakes, if using and serve!