Cook worked wonders during his first spell in charge, guiding Spireites to the League One play-offs, with some fantastic football being played along the way.
But, after seven years away and spells with Portsmouth, Wigan and Ipswich Town, he came back to a very different Spireites and with a very different mission ahead.
He came back to a club struggling to find their feet in the National League and a club looking to restore pride and regain their Football League place.
Cook began his revamp and guided Spireites to a play-off defeat against Solihull Moors at the end of the 2021/22 campaign.
But, with a full summer behind him to revamp his squad, Chesterfield stepped up their quality and pushed for the desired promotion all season.
It culminated in a heart-breaking penalty shoot-out defeat for Spireites against Notts County in front of 38,000 fans at Wembley,
Spireites had been just three minutes away from a famous victory, before County struck late to take the game into extra-time.
But it merely served to leave the promotion party on hold for another season with Spireites sweeping all before them last season to take the National League title.
In the process Spireites set a record for most club wins in the season to win the league by a whopping 12 points.
Spireites have continued that progress under Cook with a play-off semi-final defeat on their first season back in the EFL.
That journey began down at Weymouth on 12th Feb 2022, when Spireites conceded a 98th minute equaliser to draw 1-1.
But what team did Paul Cook field that day, and how many players are still in the side this season? Here we have all the answers.
5. Jim Kellermann
Kellermann left Spireites after failing to agree on the terms for a new contract and joined Woking in July 2022. During his second season at Woking, Kellermann struggled with injuries and featured only 20 times in all competitions. He left Woking to joined Ebbsfleet United, where he left at the end of last season. Photo: Getty Images
6. Manny Oyeleke
Manny Oyeleke left the club in May 2023 after struggling with injuries. He joined Wycombe on a one-year deal, before moving to National League South club Farnborough. He announced his retirement from the game in December 2024. Photo: Getty Images
7. Jak McCourt
On 27 June 2022, McCourt signed for newly-promoted Northern Premier League Premier Division side Warrington Rylands. He wasn't there long and joined Buxton in January 2023. Spells at Northern Premier League Premier Division club Ashton United, Warrington and Bradford PA followed last season. Photo: Getty Images
8. Calvin Miller
Miller had his contract terminated by mutual consent in October 2022. Miller then signed with Scottish Championship side Greenock Morton until the end of the season. After leaving Morton, Miller signed for Scottish League One club Falkirk, who he still plays for. Photo: Getty Images