This is the kind of learning that ends up as a skill - whatever the skill might be, as it were... Try to focus on sexual allusions - or hmmm maybe just practice abstinence for a while - and many expressions will sound as having sexual overtones or some kind of sexual interpretation... In Serbian, when you master something you "have it in your little finger". Here, I'd say, is the kind of learning that affects many areas or levels of memory. Like riding a bicycle or playing a musical instrument. But learning, not teaching...

I guess it boils down to this: it maybe compatible with thinking in French because the same verb can interchangeably be used by both the subject and the object (je t'apprends [l'anglais], j'apprends [l'anglais] de toi). But I don't see how "to teach by heart" could be justified in English without getting bogged down in a plethora of poetically plausible but also entirely unintended meanings ('to learn by heart' - OK, but what is 'to teach by heart' supposed to mean?) or, what's more likely, ending up as an overkill, sorry...

Formal oration, a kind of speaking that sounds like writing, has always been common. But why not try to write like you speak? Now that we have incredibly fast technology to keep up with the pace of speech — mobile phones, rather than typewriters or handwriting — that’s actually possible. What is texting? McWhorter suggests: “fingered speech.”
http://blog.ted.com/2013/02/28/the-linguistic-miracle-of-texting-john-mc...
Another spin to : je t'apprends sur le bout de mes doigts... :)