It's six points in less than a week for Gus Poyet's men, and Borini felt the victory was his side's best yet.
"This one was a lot better [than the 2-1 win at the Stadium of Light] because of all the ingredients we put into the game, the result away from home and back-to-back wins," he told SAFSee.
"It's probably our most important win of the season. To win a derby 3-0 away from home is not easy and we put in a great performance.
"Physically I thought we were much better than them throughout the 90 minutes. We were in control and didn't concede many clear chances.
"Just a few minutes after I scored the penalty we got our second goal, which was great for us."