Preheat your oven to 350 degrees Fahrenheit. Line a 9 by 9 inch baking dish with foil and spray with nonstick cooking spray.
Place the melted butter and oil in a large bowl. Stir in the sugar and cocoa powder until smooth using a wooden spoon.
1/2 cup unsalted butter, 2 tablespoons vegetable oil, 1 1/3 cups granulated sugar, 2/3 cup natural unsweetened cocoa powder
Add the eggs, vanilla extract, espresso powder, and salt. Stir to combine and then slowly mix in the flour. The batter will be thick. Stir in the chocolate chips.
2 large eggs, 1 teaspoon vanilla extract, 1 teaspoon instant espresso powder, 1/2 teaspoon table salt, 1/2 cup all purpose flour, 1 cup semi sweet or milk chocolate chips
Spread the batter into the prepared pan and top with more chocolate chips, if desired.
Bake for 21 to 25 minutes or until the brownies just lose that glossy sheen around the edges and a toothpick inserted 1 inch from the edge comes out clean. Cool before cutting.
Store in an airtight container for up to 4 days or freeze for up to one month.