The first chance of the match fell to Cavani, who received a lofted pass from Adrien Rabiot before getting an effort away, but he was unable to find the back of the net.
The home side did manage to make the breakthrough before the interval, however, when Cavani slotted the ball home following a cross into the box from Gregory van der Wiel.
Laurent Blanc's men added a second goal two minutes into the second half courtesy of Mandi, who turned the ball into his own net following Lucas Moura's headed effort.
The Parisians almost added a third through Rabiot, but the midfielder was unable to find a way past Agassa after being played through by substitute Hervin Ongenda.
A second penalty appeal was turned down by Duhamel in the closing stages of the contest when Ezequiel Lavezzi was brought down in the box, but Mandi rounded off a bad day for his side by finding his own net once more to make it 3-0 to the hosts late on.
Ligue 1's top-placed side can wrap up the title next week with favourable results.