You have to pour the pulp into a saucepan, then add a teaspoon of pectin and 3 cups of sugar. Then add a little bit of butter and a pinch of salt. Leave it to simmer for 5-8 minutes.
Anything may be used. Just keep it light and creamy so it doesn't detract from the rich, crumbly cake. If it is too heavy, the entire dessert will be ruined....
You should just throw away as it's honestly of no use after, unless you plan on making another batch. But even then I'd bite that minuscule cost and use another...
Sounds like you might just puree up some mangoes with a little sugar. I would recommend making it only in small batches, because the lemon juice is what keeps it...