Melusine is conveniently located right next to a playground so we often go there ever since we moved to the area. There are comfortable oldschool seats and sofas, it feels like being in a friend's living room. Friendly staff and reasonably quick service.
Prices are slightly high for this part of Berlin but it's all organic and homemade. I can really recommend the Vega rolls which is a homemade pancake bread kind of things rolled up and stuffed with hummus or lentil or pea spread and salad and veggies - very tasty! Costs 3,50€.
There are also extra crispy vega rolls for 4,50€ but I prefer the other ones.
Then you can get vegan rice pudding and pancakes with various toppings as well as different types of vegan cake and cookies, fresh juices etc.
There is classical music or jazz being played which adds to the slow food feeling at Melusine.
No WLAN, so no annoying laptops standing in the way ;)
Cons: slightly high prices, not all vegan yet