Level: MediumNote: Can be combined with the "Going Places" achievement. Also, you don't need to hold the Kingdom of Thessalonika title, only all its counties.
For this one start as Jarl Haesteinn in 867, who is one of the suggester characters. He can convert to French culture right from the start. You also don't have to be Catholic, you can be from any faith except Orthodox or Iconoclast. Conquer the County of Napoli which is located in Italy. You can divorce with your wife so you can get a strong ally and create some men-at-arms. After that, use the Conquer Kingdom (Thessalonika) Casus Belli.
Credit to
Bayek von Kuwaq on Steam for his
guide. Information sourced from the
wiki.