The Marseille-born di Gregorio easily dropped his rivals on the ascent of one of the most intimidating passes of the Tour and was on his own to face the two out-of-category climbs with 60km to go.
First to attack the peloton was the Saunier-Duval team, which cranked up the pace as the sprinters predictably started to suffer.
Cunego and Valverde fell behind three km from the summit and started the descent with a 45-second deficit.
A favorites' group of 17, featuring Kirchen, Evans, Ricco, Menchov, Sastre and the Schleck brothers, went down to the valley at breakneck speed.
With the help of two teammates, Valverde and Cunego came back to within five seconds of the yellow jersey pack in the valley.
But Cancellara and Jens Voigt rode a stunning team time trial that buried the Spanish champion and the former Giro d'Italia winner.
It also meant that di Gregorio, on his own against the wind, was to be swallowed as he began the final 14.4-km ascent to Hautacam with a 30-second advantage over the favorites.
Kirchen and Andy Schleck were quickly dropped and his elder brother Frank showed no mercy, stepping up another gear, taking Cobo Acebo and Piepoli with him.
The Saunier-Duval boys left Schleck some three km from the finish with Piepoli being rewarded for his previous effort with the win.
Evans, the 31-year-old Silence Lotto team leader, entered the stage six seconds behind Kirchen and rode with cuts and bruises after crashing the previous day.
In the three Tours to finish at the Hautacam, the rider who emerged from the stage up its punishing 14.4-km ascent in the yellow jersey kept it all the way to the finish in Paris: Miguel Indurain in 1994, Bjarne Riis in 1996, and Lance Armstrong in 2004.
Riders have their first of two rest days today. The race finishes on July 27.
Silence Lotto team rider Cadel Evans of Australia waves as he wears the leader's yellow jersey on the podium after the tenth stage of the 95th Tour de France cycling race between Pau and Hatacam, July 14, 2008.(Xinhua/Reuters Photo)