A good route, but not very long. While the Schmitz/Changrua book refers to this line as tricky, I did not experience any moment of trickery. I did however, get quite pumped. Perhaps the trick lies in not getting pumped?
Climb up the face just right of the tunnel on the trail and then move left under a bulge to climb up and left toward a good stalactite on the left. The crux is a hard section with less positive holds up high after you get pumped.

As you reach the Melting Wall via through the arch from Fire Wall, turn around and look on it's right side. The bolted line starting just to it's right and finishing above the path is Bonsoir.

4 bolts to a bolted anchor.