McClaren replaced Nigel Clough in the Pride Park hotseat at the end of September and believes that Saturday's performance was the best of his reign so far.
"This was one of those happy Saturdays when everything you have done in the week works out the way you want it," he said.
"There were times when it was simply beautiful to watch.
"We had to earn the right to play our football by standing up to a side we knew would be direct and physical and once we established our superiority we were terrific.
"The quality of the football for the second and third goals was fabulous and it all stemmed from having the right balance and attitude."
McClaren reserved special praise for former Reading and Bristol City midfielder Kalifa Cisse, who made his debut for the Rams after joining on non-contract terms the previous day.
"He gave us real authority in front of the back four and that provided the platform for the players in front of him to express themselves," he added.