Preheat the oven to 300 degrees F and adjust racks to the center of the oven. Line an 8- by 8-inch baking dish with parchment paper, leaving a 3-inch overhang over the sides to use as handles later. Spray the parchment with nonstick cooking spray.
Add the honey, peanut butter, brown sugar and vanilla to a small saucepan and bring to a light simmer, stirring until the peanut butter is well mixed into the honey.
Combine the cereal, cranberries, pistachios and milk powder in a large bowl and toss all together with your hands.
Pour the syrup over the cereal mixture and stir all together with a rubber spatula, working quickly because it will get pretty sticky. Add the sticky mixture to the prepared baking dish and pat down with the rubber spatula. Place a piece of parchment over the top and press down firmly. This will make slicing easier later on. Remove the parchment from the top after pressing and bake in the middle rack until just lightly golden, about 25 minutes.
Cool the bars completely in the pan, and then slice into 8 bars.