Step 1

Preheat oven to 350 F.

Step 2

Line a 13×9 baking dish with aluminum foil slings, which makes it easier to lift the brownies out once they’re cooled. Spray the foil liberally with non-stick baking spray, set aside.

Step 3

In a medium bowl, whisk the flour and sea salt together until combined. Set aside.

Step 4

In a large bowl, add the cocoa powder and espresso powder. Pour in the hot water, and whisk vigorously until smooth. Add the finely chopped unsweetened chocolate and whisk until no lumps remain and mixture is smooth and completely melted.

Step 5

Pour in the oil and melted butter, and continue to whisk until somewhat combined. This mixture will separate and look a little curdled, but don’t worry — that’s normal.

Step 6

Add the eggs and egg yolks, plus the vanilla extract, and whisk until fully combined. The eggs will help bring the mixture together, so it’ll look a lot better by now.

Step 7

Whisk in the sugar until fully combined, then pour in the flour and salt mixture. Fold the flour mixture into the chocolate mixture until no flour pockets remain and mixture is smooth. Then, fold in the chopped semi-sweet chocolate.

Step 8

Pour the brownie batter into your prepared baking dish, and bake for 30 minutes on the middle oven rack.

Step 9

Remove the brownies from the oven and let them cool for 1 to 2 hours on either a baking rack or trivet. Slice into 24 squares, and serve.