I often use the Carnation Malted milk mix in the waffle, I like the malt flavor. Sometimes I will use baking soda with, or instead of, the baking power in which case I add a 1/2 tablespoon of vinegar to activate the baking soda and it gives the waffle a sour dough flavor besides. Other berries work as well but they are harder to use, start out with the blueberries first.
I use an All-Clad square Belgian Waffle grill. Preheat the grill at a setting of 3.When it comes up to temperature brush on vegetable oil on both halves of the grill.
in a bowl add the pancake mix, baking power, and the optional malt. If you are using the malt, reduce the amount of pancake mix by the same amount. Stir in the water, a few lumps are ok, don't over mix. Now add the oil and blueberries, mix gently, the mix will be very runny.
Quickly brush vegetable oil around on all the grill surfaces. Now pour ALL the mixture into the grill, using a spoon gently push the mix into all corners and make it fairly uniform. Close the lid, the grill will have a lot of steam coming out of it for about 4 - 5 minutes.
When the grill comes back up to temperature it will beep, now gently open the grill and remove the waffle.