Preheat oven to 350 degrees F. Grease a 9x13-inch baking pan.

In a medium bowl, whisk together the flour, baking powder, salt and malted milk powder.

Using an electric mixer, cream together the butter and brown sugar on medium speed until completely combined and fluffy. Scrape down the sides of the bowl, add the eggs and vanilla, and beat until combined.

Reduce the mixer speed to low and add the flour mixture in two batches, mixing just until combined. Add the malted milk balls and chocolate chips and beat until just combined, about 10 seconds. Turn the mixture out into the prepared pan and use an offset spatula to spread it evenly.

Bake for 25 to 30 minutes, or until a toothpick inserted into the center comes out clean.

Transfer the pan to a wire rack and allow to cool for 20 minutes. Serve warm or at room temperature. Leftovers should be stored in an airtight container at room temperature for up to 3 days.