This is the French take on the surprisingly popular story of "staid grandmother becomes dope peddler". In this case: A widow hankers back to her personal belle époque when she ran a successful restaurant with her husband. Now, her husband's drunk himself to death, Asians have taken over her restaurant, her daughter is estranged and money's too tight to mention. The once lively Paulette has become lonely and depressed and blames it all on the immigrants. In true Ayn Rand spirit, Paulette then decides to use her entrepreneurial skills and sell the old ganja, even if this means cooperating with -- well, the very same criminal immigrants she dreads so much.
The story is fairly linear and takes few twists and turns, but because of the great dialogues and great acting, it's nevertheless entertaining. Like a great dish, if it tastes great you won't complain just because you've had it before. And like chocolate, I like my movies the better the darker they come.