Cook saw his side cruise to their biggest league win of the season and open up a seven-point gap on seventh-placed Rochdale, while the U’s are three points from safety.
The visitors had no answer to the speed and movement of the Spireites, who went ahead when Gary Roberts fired in a cross from Drew Talbot in the sixth minute and had a two-goal cushion after Sam Clucas finished from 10 yards in the 16th minute.
Clucas raced clear 60 seconds later to chip Chris Lewington and although Tommy Lee saved from Chris Porter, there was no way back for Colchester as Chesterfield tore them apart in the second half.
First Dan Gardner’s shot from 20 yards flew into the net off the hands of Lewington in the 59th minute and two minutes later, Jimmy Ryan was put through to lift the ball over the goalkeeper.
Lewington brought down Roberts, who tucked away the penalty five minutes from time to complete a memorable night for Chesterfield and a dreadful one for Colchester.
But Cook said: “Sometimes you have to show some manners; it’s a disappointing night for Colchester who had big moments in the game and everything has gone our way tonight.
“It was one of those nights when everything went our way so while we are happy with what we’ve done, we must also wish Colchester the best of luck for the rest of the season.
“Tonight was everything I like about the game – the energy levels were good out of possession and in possession we moved the ball well and we’ve seen the results of a fantastic team performance.
“I think it’s common knowledge we are a good side but there’s a long way to go and other teams can still catch us so it’s not sorted out.
“But what it does is keeps our supporters interested and we have a habit of finishing seasons strong so if we can keep the momentum going the likelihood is we can get there ”
U’s manager Tony Humes said: “Massive credit to Chesterfield, they were absolutely outstanding but we were nowhere near. We knew they are a good team and we knew they were going to come at us but it’s up to the players to deal with that and I can’t defend anything that happened out there.
“We have been played off the park by a very good team who wanted it more and had every single player working their socks off whether they had the ball or didn’t have the ball, and we didn’t have it.
“Chesterfield had the determination and desire that a football player going out on the pitch doing his job should have.
“I’ve said to the players that if they are going to have a career in the game they’ve got to be as Chesterfield were and that comes down to hunger, desire and work rate.”