In this world, witchcraft is practiced openly and is a neccessary function of society. Men cannot use magic directly, but possess much more mana than women. There are some spells that a witch may not have the neccessary amount of mana to perform, or it would be extremely difficult for her to do it herself. During intercourse, a witch can absorb the essence of a male and use it to temporarily power her own spells, or to concieve a child.
In many fantasy writings, sex is used as a neccessary part of performing magic. It often feels like it is thrown in just as an excuse for having it, and can come off as tacky or cringeworthy. How can you make it feel natural to a setting? How much should you show and tell? Should you go into detail about how it works, as well as its limitations? Or should you gloss over the nooks and crannies of it and leave it to the imagination of the reader?