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.
1. Scott Loach
Loach joined Derby as back up keeper in July 2022. Loach spent the 2023/24 season as third choice keeper and failed to make a first team appearance. He retired from football in May this year after making over 500 appearances to concentrate on a coaching career. Photo: Getty Images
2. Fraser Kerr
Kerr was released at the end of the 2021/22 season and signed for York City. He was released by York after one season and joined AFC Telford United in July 2023. Kerr left the club at the end of the 2023/24 season to move abroad. Photo: Getty Images
3. Jamie Grimes
Jamie Grimes has been there every step of the way under Paul Cook's transformation of Chesterfield. Grimes scored a brace against Boreham Wood in order to secure the Spireite's promotion as champions back to the Football League. He is still at the club but is expected to leave in the summer. Photo: Getty Images
4. Alex Whittle
Whittle was released by Chesterfield at the end of the 2021/22 season, before joining York City later that summer. He is currently at National League South side Yeovil Town. Photo: Getty Images