Our 5 mos. old puppy is left at home during the day while we are at school/ work. She has an ex-pen with her bed, food & water, pee pad and LOTS of toys.

Still we are sure she gets bored, so I try to leave her a Kong filled with treats so she has one more thing to do/ keep her busy. We've been stuffing it with a mix up broken up biscuit type treats and her regular kibble. I pack it as tightly as possible and she likes it, but I suspect it doesn't take her very long to get to the goodies. We can't use peanut butter to stuff it because my daughter has a severe peanut allergy. I haven't actually looked at it but I suspect the stuff Kong sells to stuff the toys with is the equivalent of human 'spray cheese'- full of not-so-good stuff.
What do you think of the idea of grinding a mix of her biscuits and food in the food processor and mixing with water to form a paste and stuffing the Kong with that? (Thought I might freeze it too.) Do you think that will work? Would that be ok? If not, any better suggestions?
Thanks!