The Premier League side outclassed their Serie A counterparts throughout the encounter and grabbed an early foothold as defender Wesley Fofana opened the scoring mid-way through the first half. Pierre-Emerick Aubameyang and Reece James furthered Chelsea's lead to help Graham Potter's side clinch back-to-back victories for the first time this season.
"Delighted with the performance and attitude against top opponents," Potter said. "I thought we had to react well and we did. We had to suffer as well which is good to do. I'm really pleased for the players and that's a good start for us.
"Chelsea versus AC Milan is a fantastic football match and to be involved in it is something I'm grateful for, but to win the match is great. We need to recover now and go again at the weekend."
And Potter's side struck first through summer signing Fofana. The Frenchman swept home the loose ball from a corner which caused havoc in the Milan penalty box, scoring his first goal since signing from Leicester City in the summer.
Fofana, though, was forced off through injury 14 minutes after opening the scoring.
Potter said afterward that Fofana would have a scan on the injury on Thursday.
"We don't know yet [how bad it is]," he said. "That's the one disappointing thing on the evening. He needs a scan tomorrow and fingers crossed. I wouldn't want to speculate on it, but we're concerned, and we'll have the scan tomorrow."
Aubameyang doubled Potter's side's lead 11 minutes after the break, tapping home James' cross as Fikayo Tomori failed to defend the cross.
Chelsea boss Potter hailed Aubameyang in the week, saying the striker conducted himself "perfectly" since the horrific robbery which left him with a broken jaw in August. The striker hadn't seen too much of the ball until his clinical strike which gave Chelsea a two-goal cushion.
Six minutes later, the provider turned goalscorer as James received the ball in the box and fired home past a hopeless Tatarusanu after yet more poor defending by the Italian side.
"Reece is a fantastic player, and a young player," Potter added of the 22-year-old. "He's developing all the time and will get better and better. I've really enjoyed working with him, he's got a lot to offer. He can play in any game in the world, he's tremendous. My job is to try and reach his potential, as his potential is beyond the sky.
"We love him, he's so important for us. He could be a Chelsea legend with anybody."
A lacklustre Milan failed to threaten Chelsea in the closing stages as Potter's side ran out comfortable victors.
"We could've played better, it's clear our opponents played at a very, very high level but our accuracy wasn't as good as it should've been," Milan coach Stefano Pioli said. "After a couple of minutes we started doing things we weren't meant to be doing and our opponents could exploit space behind us quickly.
"It wasn't a good evening, this is just an episode. We weren't dangerous at all and didn't do enough in front of the opposition goal. It wasn't our day today. We knew it was going to be a tough game, but mentally, we didn't play as a team."