Kristin Cavallari Out For Steamy Date Night with New Boyfriend Mark Estes

Kristin Cavallari's lookin' head over heels for her new man Mark Estes, holding hands and flashing sweet looks on their way to dinner in L.A.

The happy couple strolled into Sugarfish -- a classy sushi joint in ritzy Beverly Hills ... and KC was dressed to impress, hot leather pants pulled up high.

The couple grabbed a bite to eat before having a car pick them up ... and, Cavallari even helped a pap figure out who the 24-year-old looks like -- pointing to one legendary actor.

Watch the clip yourself to hear the comparison ... and, check out the demeanor too. Lots of laughin' and flirtin' -- great to see the new couple's still in that honeymoon phase.

Remember ... Cavallari went public with her relationship not long after we posted photos of her and Estes hangin' out down in Cabo -- lookin' fabulous while riding a tram at the airport headed for customs.

Cavallari's since detailed more specific info about her new dude ... taking to her podcast to talk about how fate seemingly brought the two together.

And, the happy couple seems to be gettin' serious -- 'cause Cavallari shared a snap where Estes appeared to be deep in convo with one of her three kiddos ... definitely looks like more than just casual dating.