If you thought you couldn't make fudgy brownies without a box mix...you were wrong.
Preheat your oven to 350 degrees F. Grease an 8x8 square pan or line with parchment paper. Set aside.
In a large microwave-safe bowl, melt the butter and 1/4 cup chopped chocolate or chocolate chips in 30-second intervals, stirring in between, until melted and smooth. This took about 1 minute in my microwave.
Whisk in the sugar. If the mixture is really hot, let it cool for a minute before whisking in the eggs one at a time (you don't want to cook the eggs!), until fully combined.
Whisk in the espresso powder, vanilla, salt, and cocoa powder until the mixture is smooth and well-combined. Stir in the flour just until the mixture is smooth and you no longer see clumps - but do not overmix, and don't use a mixer. We don't want to incorporate too much air in the batter, or the brownies won't be fudgy.
Stir in the chocolate chips, then scrape the batter into the prepared pan. Bake for 30-32 minutes, until a toothpick inserted in the center comes out clean or with a couple crumbs attached.
Sprinkle coarse sea salt over the top, and serve brownies warm, preferably with a generous dollop of vanilla ice cream.
*the espresso powder will not make the brownies taste like coffee - it enhances the chocolate flavor. You can buy it at most grocery stores in the baking aisle, or on Amazon.
Brownies will keep, well-wrapped at room temperature (I pack them tightly in a tupperware), for up to 5 days.