Preheat the oven to 350 degrees F. Generously grease a loaf pan with nonstick cooking spray or butter. Line with a strip of parchment paper so that it hangs over the narrow ends of the loaf pan.
In a large bowl, whisk together the milk and peanut butter until well blended. Add the flour, sugar, baking powder and salt and fold to combine. Fold in the peanut butter chips.
Pour enough batter into the prepared loaf pan to fill it halfway up the sides. Place an even layer of chocolate bars on top of the batter and then top with the remaining batter. Bake until a cake tester comes out just clean, about 40 minutes. Let cool for 1 hour, then remove from the loaf pan.