In a small microwavable mixing bowl, add in the chocolate and butter. Heat in 30 second intervals, stirring in between until chocolate and butter are well combined and smooth.
Whisk together the egg and sugar in a separate bowl until pale in color; this took me 3-4 minutes. Gently stir in the melted chocolate into the egg mixture.
Stir in the sea salt. Place the bowl of molten chocolate in the fridge while you make the peanut butter bread.
Preheat the oven to 350 degrees. Spray a 9x5 loaf pan with nonstick cooking spray.
In a large mixing bowl or stand mixer, add milk, eggs, sugar, and peanut butter and mix on high until smooth. Add the remaining bread ingredients and mix until well incorporated.
Pour batter into the prepared 9-x-5-inch loaf pan.
Remove chocolate from fridge.
Using a spoon, create a little pocket in the middle of the peanut butter bread batter for the chocolate. Don’t stress, the batter will sink in. As you are creating the pocket in the batter, spoon the chocolate into the middle of the bread, creating a row of chocolate right down the center (see picture).
Using a butter knife, carefully spread some of the peanut butter bread batter over the chocolate, to enclose the molten chocolate center. Don’t stress for perfection, it will still turn out and taste amazing.
Bake for 55-60 minutes. Let the bread rest and cool for 15 minutes before removing it from the pan. Enjoy!