I never remember to leave the cream cheese out on the counter to soften, so I pop it in the microwave for 30 seconds. That usually makes it soft enough to work with.
Combine the softened cream cheese with the peanut butter in a small bowl. Do not attempt to whisk this concoction. It has the approximate constitution of concrete, and it's nearly impossible to whisk. Get out a nice, sturdy spatula and fold it together. I figured that out shortly.
Pour in some milk. If you add 1/4 cup, you will get a frosting consistency. Though it wasn't what I wanted, it does have some good points. For one thing, it's easy for kids to spread on the waffles (rather than dipping). Allie really liked spreading it, picking up little pinches of it, and throwing it around the dining room. (Clearly, she wasn't hungry enough.)
When you have the peanut butter, cream cheese, and milk well combined, add in the powdered sugar and vanilla. Mix well.
Heat waffles in the oven or toaster and cut them apart.
To serve, scoop some of the peanut butter mixture in a dish with 2 Wafflers sticks.