This kind of wild fruit that would turn black in the mouth had several different names. It could be called wild peony, southern candle seed, black rice seed, charcoal mother, black nightshade, cloth ion, black nizi, purple eggplant, ground twist, longan grass, black star, wild eggplant, black girl, black sky naked, wild pepper, mountain spicy eggplant, lantern pearl grass, wild pepper tree, seven grain button, black furuncle grass, ground bubble seed, ground gourd grass, mountain pepper, wild sea pepper, red nan, wine pot seed, and so on. These names may vary from region to region, but they all refer to the same wild fruit that turns the mouth black.
If 'black ceampie' is a regional or new type of dish, perhaps it could be a dessert with blackberries and some sort of creamy filling. Maybe in a small village, there's a story of an old lady who made the best 'black ceampie' and everyone in the village would gather for it on special occasions. However, this is all speculation as the term is not common.
One example could be a story where Regulus Black struggles with an eating disorder secretly while trying to maintain his Slytherin image. Maybe he uses magic to hide his symptoms from others at first.
I'm not sure of a specific fanfiction on this topic. However, you could start by looking on major fanfiction platforms like Archive of Our Own. Search for 'Sirius Black' and 'eating disorder' in the search bar. There might be some stories that deal with this in a sensitive and interesting way.
You can start by showing his internal struggle. For example, his thoughts about food, body image, and self - worth. Let the readers see how he rationalizes his disordered eating behaviors.
One possible plotline could be Sirius struggling with the disorder in secret while trying to maintain his tough exterior in the wizarding world. Maybe he's using it as a way to cope with the stress of his family situation and his time in Azkaban. His friends might start to notice small signs like his lack of appetite at meals or his weight loss, and gradually try to help him.
As I'm not entirely sure what 'black ceampie' is, it's hard to give stories from different cultures. But if we assume it's a food item, different cultures might have their own interpretations. For example, in a culture that values dark - colored foods for their supposed health benefits, 'black ceampie' could be a part of their traditional cuisine with a story about how it was discovered to boost immunity.
The Legend of War Tiger fits the plot you described very well. After the solar eclipse, the main character returned to the War of Resistance, and the plot related to the black snake and the white toad was also involved. I recommend this novel to you. I hope you like it. Muah ~