Billie Eilish & Jesse Rutherford Grabbed Romantic Dinner Solo This Week

Billie Eilish and Jesse Rutherford are definitely a thing -- 'cause they pretty much recreated the classic "Lady and the Tramp" date scene ... loving gazes and spaghetti included.

The two singers were out for dinner Thursday night at a vegan joint in L.A. called Crossroads Kitchen -- and they had a booth all to themselves for the lengthy meal ... as you can see in these new photos, obtained by TMZ.

Eyewitnesses tell us Billie and Jesse were there for at least three hours, if not longer -- leaving the place a bit before midnight and apparently arriving before 8:30 PM. Unclear what Jess was eating, but it looks like BE went with pasta ... slurping up some of the noodles.

We're told there was some PDA between Billie and Jesse as well -- including some smooches in between bites. Obviously, they kept that lovefest going into Friday, where they were seen at Universal Studios' Halloween Horror Nights.

As we reported ... a viral video showed Jesse and Billie walking out of a haunted house together, and grab hands as they strolled away. Her brother, Finneas, was with them too.

While it was somewhat unclear if they were actually romantically involved from that clip alone, this all but confirms they're an item ... something Twitter doesn't seem too keen on, based on the many reactions online.