Preheat oven to 350F. Butter the bottom and sides of a 9×13 inch metal baking pan. Put a long piece of parchment paper in the bottom of the pan, letting the parchment extend up two sides of the pan and overhang slightly on both ends. Place another piece of parchment paper in the same manner, perpendicular to the first sheet. (This will make it easy to remove the bars from the pan after they have baked.)
In a medium bowl whisk together the flour, baking powder, salt, cinnamon and nutmeg; set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat together the butter and brown sugar on medium speed until light and fluffy, about 5 minutes. Add the eggs one at a time, and then the vanilla. Beat, scraping the bowl, until thoroughly combined. On low speed, gradually add the flour mixture until just combined. Give the dough a final stir with a spatula or wooden spoon to make sure the flour is incorporated. Fold in cinnamon chips
Transfer the batter to prepared pan; using spatula, spread batter into corners of pan and smooth surface (batter will be thick).
To make the topping, in a small bowl combine the granulated sugar, cinnamon, and nutmeg; sprinkle evenly over the top of the batter.
Bake for 25-30 minutes or until the surface springs back when gently pressed. Transfer pan to wire rack to cool completely. Using parchment overhang, lift brownies from pan and cut into 2-inch squares. Store in an airtight container at room temperature.