First thing's first: Petrohue IS off the beaten path. The way you get there is by taking one of any buses in nearby cities (we took the bus from Puerto Varas) that say Petrohue. It is definetly worth going to, although unless you plan to take a boat or do a lot of hiking there, a few hours suffices.
On this place, apiculture is huge. They've got this treatments with bees, and they're suppose to make you feel good. They get the bees and let them sting where it hurts. Don't know hot it works, but I've heard that it does.
Now, if you're not interested in getting sting by bees, then I'd recommend you to buy honey. Why is this honey so special. Because the bees take the juice out of the flower of the ULMO tree, and the honey is remarkable. It tastes somehow different. Sweeter. You cannot leave without buying ulmo honey bee.
The place is on the way from Puerto Varas to Petrohue, on Ensenada. It's next to the road, so it's hard to miss.