Preheat the oven 350˚F. Grease an 8 inch square pan and set aside.
In a medium saucepan, melt the butter, whisking frequently. Watch for brown specks and nutty aroma.
Once the butter smells nutty, pour into a large bowl to stop the butter from cooking.
In a separate bowl, mix together the flour, baking powder and salt.
Mix in the brown sugar to the butter. Beat in the eggs and vanilla. Slowly mix in the dry ingredients until just combined.
Pour the batter into the prepared pan and top with peanut butter chips.
Bake in the preheated oven for 20-25 minutes, or until a toothpick inserted in the centre comes out mostly clean.