The full classic route takes 7-10 days between the Parvati Valley near Manali and the Pin Valley in Spiti. I did a shorter version of this trek hiking up to the pass from Mud in the Pin Valley and then returning back the same way. Although much of the better scenery of this trek is probably on the Paravati Valley side approach to the pass, I was hesitant to do this full trek on my own due to the duration and the aforementioned security issues of trekking in the Paravati Valley. Hiking up to the pass is a nice short but strenuous hike from Mud. From Mud hike up the dirt road along the western side of the valley. Eventually you will reach a junction of three valleys continue down the western most valley on the northern side of the river. The trail is good and well marked until the point at which you need to cross the river. I camped on a grassy section near a spring just before the river bends to the north and is joined by another stream that flows from the Pin-Paravati Pass. At this point you need to either ford the river or continue to the north and cross over the glacier from where the river flows and then hike back from the other side of the river. On the other side of the river the trail is nearly nonexistent from what I could see. I ended up just reading the terrain and hiking up the easiest path I could. There are a series of grassy meadows and plateaus where it is possible to camp on the north side of the stream that heads up to the pass. I hiked up just before the terrain turned rough and camped a second night there. It was only about three to four hours of walking but the weather turned bad and I road out a snow storm that afternoon and night. There is little in the way of a path and after a fresh foot of snow pretty much no path. Just head up the snow field to the lower right of the large peak at the head of the valley. There are a few prayer flags marking the pass which is a long walk over the snow field. Its possible but long to return down from the pass to Mud in the same day.