1-Adjust the oven rack to the middle: Adjust the oven rack to the middle position, preheat the oven to 350°F, then spray an 8 1/2-4 1/2-inch metal loaf tin with flour-based baking spray. Line the loaf tin with a parchment paper sleeve (to help remove the brownie bread after baking).
2-Add the semi-sweet chocolate to a medium,: Add the semi-sweet chocolate to a medium, microwaveable bowl, then microwave at 1-minute increments until melted and smooth. In a separate microwaveable bowl, melt the unsalted butter as well, but in 30-second increments until melted. Set both aside to cool down slightly.
3-In a medium bowl, whisk together the: In a medium bowl, whisk together the all-purpose flour, dutch process cocoa powder, baking soda, and salt.
4-In a separate large mixing bowl, using: In a separate large mixing bowl, using your hand mixer (or stand mixer), beat together the eggs and granulated sugar on medium-high speed until light in color, fluffy, and almost doubled in size (takes about 4-4 1/2 minutes).
5-Mix in the melted chocolate, milk, and: Mix in the melted chocolate, milk, and vanilla extract until mostly combined.
6-Fold in the dry ingredients to the: Fold in the dry ingredients to the wet ingredients with a spatula, then add in the melted butter.
7-Pour the brownie bread batter into the: Pour the brownie bread batter into the prepared loaf tin. Optionally, you can top with a few semi-sweet chocolate chips. Bake for 55-60 minutes at 350ºF, or until a toothpick inserted into the center of the brownie bread comes out with a few moist crumbs but no wet batter.
8-Allow the brownie bread to cool inside: Allow the brownie bread to cool inside the loaf tin for about 15-20 minutes before transferring it to a cooling rack to finish cooling. Leftover brownie bread can be stored at room temperature for up to 3 days, wrapped in plastic wrap and (optionally) an extra layer of aluminum foil. To freeze, let the bread cool completely, then slice. Wrap each individual slice in plastic wrap 1-2 times, then keep it in a freezer-safe container.