Goals from Jake Buxton, Will Hughes and Chris Martin handed the Rams a comfortable win over a Wednesday side who have just one win to their name this season.
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.
County took the lead just before the break as Jamie Ward's left-wing corner was met with a thumping header from Jake Buxton.
And it took the Rams just three second-half minutes to underline their dominance with a second goal. They carved through Wednesday's defence and a low cross from Craig Forsyth left England under-21 midfielder Hughes to tap in from two yards at the far post.
It was over as a contest 10 minutes later when Ward provided the cross from the right and the impressive Chris Martin swept the ball in from close range.
Wednesday claimed their only win so far this season as they dismantled Reading 5-2 at Hillsborough last week but Dave Jones was left fuming with his players' performance in the midlands.
"I really didn't see that one coming after an electric week in training," he said.
"Unfortunately, far too many of our players lost their personal battles. Too many seemed to think that after putting five Past Reading a week ago we only had to turn up for it happen again.
"I am as angry as I have been in a long time. Derby didn't have to earn it. We gave it to them.
"There was a complete absence of communication for their second and third goals. Derby were allowed to walk the ball into our net.
"No doubt there will be people in the dressing room saying 'It wasn't me. It wasn't me.' But the video won't lie."