Turns out I had a mulberry tree growing near my apartment the whole time. While it would have been nice to have a few more mulberries for the filling, it still came out good with this recipe:
Well, I don't, this was just luck. These all came from a tree near my apartment that my girlfriend spotted. She noticed them when they were unripe and went out as soon as they were ready but she definitely had competition from the birds.
Edit: she mentioned that the tree was near the road by a bus stop, so the traffic may have kept them from eating too many of them
Growing up we had two large mulberry trees in the yard, and every summer I was sent out daily to pick a bucket full of mulberries. My Mom made mulberry syrup, mulberry jam, mulberry clafouti, put them in fruit salad, and, of course, made mulberry cobbler.