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.
9. Liam Mandeville
Liam Mandeville played a key role in Chesterfield's National League title win and was named in the league's team of the year. Mandeville showed his versatility by playing at right full back as well as his more usual attacking midfield and forward roles throughout the season. He is still a key part of the Spireites side who made it to the League Two play-offs. Photo: Getty Images
10. Akwasi Asante
Akwasi Asante played little in the second half of the 2022/23 season and not at all in 2023/24 due to injury. He left the club by mutual consent on 8 November 2023, before signing for Darlington. His contract was cancelled by mutual consent in May 2024 and he is currently without a club. Photo: Getty Images
11. Kabongo Tshimanga
Tshimanga joined Peterborough United in January 2023 after agreeing a loan deal until the end of the season ahead of a permanent transfer in the summer. Loan spells at Fleetwood Town and Boreham Wood followed. He was transfer-listed in May 2024 and joined Swindon Town on loan in August 2024. It turned into a permanent deal with Tshimanga scoring 11 goals last season. Photo: Getty Images