Preheat the oven to 350˚F. Lightly spray a loaf pan with cooking spray.
Bread: In a medium bowl, mix together the flour, sugars, baking soda, baking powder, salt, cinnamon and the all spice. Make a well in the centre of the mixture.
Put the peanut butter in a microwave safe bowl and microwave for around 30 seconds, or until melted. In a medium bowl, combine the banana, oil, eggs, vanilla and peanut butter until fully combined.
Pour the banana mixture into the flour mixture. Mix slowly until just combined.
Pour the batter into the prepared pan and bake for 50 minutes, or until a toothpick inserted comes out clean.
Let cool in the pan for 20 minutes, then remove to cool completely on a wire rack.
Glaze: Melt the peanut butter in a small bowl, and whisk in the powdered sugar and milk. Drizzle the glaze over the cooled bread.