While visiting the Musée d'Orsay with Paul Verdun, Hassan is struck by Paul Gauguin's The Meal. The subject matter is really simple: Three people at a table with some simple food (we're talking banana-caliber simple) on top of it. As Hassan looks at the painting, he has his epiphany that the simple way is the best way. There's nothing overdone or imposed on the subject matter of the painting—it is totally minimal—so the painting is a symbol that true artistry is being able to master an object as it is, without all the bells and whistles.
The people in this painting aren't in a top-tier restaurant getting ready to start their third course, and the food in front of them hasn't been cooked up to the point of the ingredients no longer being recognizable. The food is simple and clear, and each fundamental ingredient takes the spotlight in its own right without being dolled up. And since this scene is hanging in a museum, it's validated as good.
In short, the painting is symbolic of the major culinary turn Hassan takes—he goes back to basics in a big way—and, in reminding us of this, also reminds us that his biggest success comes when he follows his own path. Not too shabby for a bunch of bananas.