The 18-year-old has been loaned back to the Saints until July which allows him to finish his Leaving Cert and gain more experience at home before relocating to Italy.
Abankwah is moving for a substantial six-figure sum with the potential for the deal to be worth more than €1m to the Saints in time.
He made 13 appearances for the Saints last term, including coming off the bench in the FAI Cup final.
"I'm buzzing and absolutely delighted," said Abankwah, speaking to the Saints website from Italy, after a signing a deal with the club until the summer of 2026.
"I found out last week about the interest, flew out on Monday, had my medical on Tuesday and signed today so I'm really looking forward to it. The people here are lovely, they've been very welcoming the city is very nice.
"I'm looking forward to getting going and still have a big six months at St Pat's and my Leaving Cert.
"I feel very happy right now, I'm lost for words."
Need a VPN? Or seeking to switch? Then support Tribal Football by clicking here to sign up with our official partners NordVPN. Not only will you receive the best VPN experience, but also great discounts by signing up via Tribal Football. Thanks for your support!