Back when I was in high school a friend of mine begged our French teacher (a very proper NZ lady) to tell him some swear words in French. She then told him a phrase which he gleefully repeated forever after. The phrase in question was pronounced like this:
Fashay twa, poofkot!
(This is rendered phonetically as best I can, because I never saw it spelled. The “twa” is, I’m assuming, “toi.”)
What did this phrase mean in English?
-Ben
Fashay is most likely Vas-y which means go away.
Not good at French but all the WAGs are coming from the Alternative French Dictionary and insults.net:
Fashay twa:
“baise-toi = f*ck you.”
As for poofkot! It could be:
“bouffon = asshle."
Or:
"pousse-crotte (masc. noun) = push-sht homosexual - for men only.”
Or:
"putain
All the quotes are coming from the references.
Here are my guesses. [bragging]I speak as someone who has actual experience in insulting people in French.[/bragging]
Fashay twa: This could be “va chez-toi” which means go home, but without being overly polite it’s too nice to be considered an insult. A better guess could be “Va chier, toi” or “go take a shit, you.” “Va chier” is a common way to tell people to f*** off, but here the final “toi” is kind of out of place gramatically speaking.
poofkot I’m almost certain that this is “pauvre con”, as it is one of the most common French insults. Roughly, it means “poor fool” but “con”, the quintessential French insult, is a lot stronger than “fool”. For the etymologically-enclined, “con” is derived from the same root as the English “cunt” and is often used in that meaning in pre-WWI erotica.
GIGObuster mentioned a few other possibilities but I think they’re unlikely.
“Baise-toi” sounds like a litteral translation from English, I’ve rarely, if ever, heard it.
“Bouffon” is kind of weak, like the English “buffoon”.
“Pousse-crotte” is good, but seldom used. In a French Cursing for Foreign-Language Speakers class, I’d place it in the intermediate to advanced course.
“Putain” is another quintessential French swear word, but phonetically, it doesn’t fit nicely with Ben’s sentence.
“Trou du cul” is also very common, but again, it’s a long way from “trou duc’” to “poofkot”.
French is such a great language when it comes to cursing. In my opinion, one of the best aspects of French cussing is that it’s very easy, with a little imagination, to create new insults. So really, the possibilities are almost endless. (If you’re really confident in your level of French proficiency I suggest almost anything by San Antonio for good examples of made-up cussing. He is the master of the art.)
BTW, it could be that your teacher was simply giving you nonsense. Japanese kids would often ask me for bad words in English. I usually taught them really mild ones, like “fool” because I knew they would repeat them over and over again. How puritan of me! 
Actually, I’m assuming the insult was something mild, like, “Leave me alone, annoying fellow!” My friend didn’t know what it meant, but assumed it was on the level of “go felch a goat, goat felcher!”
I think “va chez toi” is almost certainly the “fashay twa.”
-Ben
I agree with jovan’s very thorough analysis :), but I think that it is likely that the “pofkot” meaning “pauvre conne”, the feminine form, feminine forms often considered somehow more insulting.
If the woman were really such a proper lady (ahem, like myself, for instance), she may well have given the young man a very mild insult. (Speaking as a teacher who once convinced a class of remedial Français that “Zut de flute” was an unspeakable expletive). By the way, I ran into a former student from that class recently at a movie opening. He said hello, couldn’t remember my name, but he said “zut de flute” and laughed. He is now a talent scout. Something to do with movies. Goes to show something.
No, baiser means to fuck as in to have sex. It is not the equivalent of fuck as used in English. That would be Foutre, as in Tu va te faire foutre stupide sale espece de merde. I’m not sure how I might translate baise-toi but I can’t recall ever hearing it either.