I think you need to consider that the reason you can't find any writing on this is that it simply does not appear in the historical record. Historians can only research the information that actually exists.

The major stumbling block to the scenario you're proposing is the way that class and gender intersect. In the stereotypical situation of employer/servant relations, with a male employer and female servant, the class dynamic and the gender dynamic combined created a massive power imbalance in the employer's favor. (Though it's important not to neglect the sexual violence perpetrated by male servants against female ones, which appears very frequently in court records.)

The upper classes were conditioned to see all servants as lesser orders of being, people whose needs could be and indeed should be easily disregarded as sacrifices to their own comfort: they should wake up before dawn to have breakfast ready when the master wanted it, go to bed after midnight in order to finish cleaning up after the dinner party, walk miles in the cold to bring them a coat.

It would be a flattening exaggeration to say that men saw women as a lesser order of beings at this time, but they did generally see their needs for independence, self-expression, and emotional support as being of a greater priority than those of the women in their lives, and women expected to subordinate themselves to their husbands (even if they had the possibility to control their own property after marriage, something that had only recently been given to them).

So when you layer these two things together to look at cross-class heterosexual relationships in this period, the picture is very problematic. Upper-class men were doubly entitled when it came to the time, attention, and bodies of female domestic servants, because they were employees and because they were women. At the same time, upper-class women and male servants were in a more awkward position: the respect that a woman was supposed to have for a man conflicted with the respect that a servant was supposed to have for his employer. Both were well aware that romance for these young ladies was supposed to go along with potential marital prospects, and that there was absolutely no chance of that.

So very few upper-class young women would look at male servants with enough humanity to feel much personally for them, let alone fall in love, let alone do so to such an extent that they would allow themselves to act on it or write about it in such a way that it would end up on the historical record.