The Dane has agreed a three-and-a-half year deal - with the club holding an option to extend the deal further - after moving to the top of the Premier League 2 division two scoring charts with his goal against Sunderland last week.
Sørensen has also scored in all four of Newcastle's Checkatrade Trophy ties this term, and is set to wear the number nine shirt in Tuesday night's Northern Section quarter-final against Sunderland's first team at the Stadium of Light.
The 19-year-old joined Newcastle from HB Køge in the summer of 2016, having become the Danish side's youngest ever debutant when he came off the bench in a First Division game against Silkeborg IF.
Sørensen told NUFC TV: "It means a lot - I've worked hard for it over the last three years or so and I'm delighted to sign with such a massive club.
"I think I've done well this season and when you do well, you get your rewards. I work hard in training every day and it paying off is just massive."