Line a standard loaf pan (8 1/2 x 4 1/2 x 2 1/2 inch) with parchment paper for easy removal or grease pan.
In a medium sauce pan melt the butter, then add both the granulated and brown sugars and mix. Remove the saucepan from the stovetop and cool for 5 min.
Add in the vanilla extract and the egg. Mix well.
To a medium size bowl add sifted cocoa powder, flour, salt, espresso powder, and baking powder. Mix well then add to butter/sugar mixture and mix.
Gently fold in 1/4 cup of the chocolate chips.
Spread batter into loaf pan and top with remaining 2 Tbsp of chocolate chips. Batter will be thick.
Bake 25-30 min or until a toothpick inserted in the center comes out clean.
Sprinkle lightly with flaky sea salt if desired.
Notes
Can use regular All-Purpose flour in place of GF Flour.
Can use vegan butter and make it dairy-free.
You can use a larger bowl to melt the butter in the microwave instead of the stovetop.