Booker, 25, and his Phoenix Suns were eliminated from the playoffs by Luka Doncic and the Dallas Mavericks in a shocking second-round upset. The Suns were the favorites to win the championship this year after they ended the regular season with a substantially better record than any team in the league.
The couple, who are rarely photographed together, held hands as they headed to dinner wearing matching all-black outfits.
Jenner seemingly made an ode to her sister and soon-to-be husband's signature rocker style in a goth-inspired sheer tea-length skirt, adding a strapless corset-like top, peep-toe pumps, and a statement choker with a large red cross to complete her look.
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The NBA all-star complemented his girlfriend of nearly two years with a casual, monochromatic ensemble of his own, sporting black pants, a black shirt, and a black bomber jacket as the couple made their way to Ristorante Puny in Portofino, where the Kardashians, Barkers, and other loved ones dined in celebration of the lovebirds' upcoming nuptials.
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"You can feel all the love. Everyone is very excited to celebrate Kourtney and Travis," a source tells PEOPLE.
"They have a special menu with Italian wine, hand-made trofie al pesto pasta, sea bass and coffee parfaits. The menu is decorated with a heart."
The insider adds that romance is in the air, "It's a beautiful evening, Kourtney looks gorgeous!"
This is the second time the A-List couple has jetted away to Italy for a romantic trip. Booker and Jenner spent time in the country last summer after he and the USA Basketball team won the gold medal in the Tokyo Olympics.
Booker and Jenner made their relationship public on Valentine's Day in 2021, but rumors of their romance began in 2020.
In October of last year, a source close to the reality star told PEOPLE that she's "crazy about him" and the entire Kardashian bunch "loves" him.