Tammy Abraham had put the Blues ahead with an intelligent finish for the hosts early in the first-half.
Havertz then made it 2-0 after 28 minutes before Ross Barkley put the game to bed just four minutes after half-time.
Then it was time for Havertz to put an exclamation mark on his third appearance for the club by netting another two goals in the space of ten minutes.
Blues supporters were also able to watch new arrivals Thiago Silva and Ben Chilwell make their debuts for the club.
And speaking after the game, Lampard was delighted with the all-round performance from his side.
"It was a very good night in those terms," he told a post-match press conference.
"I knew it would be a tough game, but today I wanted it to be about how we can work off the ball. We saw elements of that. All the individuals and the minutes and the fitness. It was a positive night for that."