Mob-connected Nassau County detective Hector Rosario tried to sic authorities on a rival family’s illicit gambling den — and even told local prosecutors the coffee-connected password to get inside, witnesses testified Thursday.

The cop — allegedly on the take from the Bonanno crime family to the tune of $1,500 per month — walked into the Nassau County District Attorney’s Office and told them the secret saying to get into the underground casino at the Gran Caffe Gelateria in Lynbrook, DA Det. John Clinton said in Brooklyn federal court.

“You go by the counters, ask for an espresso or cappuccino [and] say you knew someone named Kelly — and you would be able to go to the back,” Clinton told the jury as he recounted his conversation with Rosario.

Rosario also told authorities about the building’s doors, security cameras and gambling machines — but that aroused prosecutors’ suspicions, since he wouldn’t tell them exactly how he knew.

The ex-cop said something about an informant who tipped him off — but demurred when Clinton asked the meet the source and said it wasn’t possible, the detective testified.

Rosario, 51, also offered up info about Salvatore “Sal the Shoemaker” Rubino’s gambling parlor, which was affiliated with the notorious Genovese crime family and operated out of Sal’s Shoe Repair, Rubino’s store in Merrick, Long Island.

For good measure, he also ratted out another illegal mini-casino in the South Shore Bridge and Chess Club run by the Gambinos.

Clinton offered to let Rosario in on the investigation, but the detective waved it off — which Clinton testified was “a little unusual.”

An FBI agent, Orlando Tactuk, later buttressed Clinton’s testimony when he told the court Rosario ducked his questions during a January 2020 interview — including inquiries about several underground gambling spots and whether he had a business relationship with Sal Russo

Rosario, 51, has been charged with obstructing a grand jury probe into racketeering and lying to the FBI as he allegedly conspired to target rival Genovese and Gambino Mafiosos during a feud that erupted after a profit-sharing scheme between the families went south.

On the trial’s opening day, prosecutors introduced jurors to a laundry list of alleged mobsters and mapped out a constellation of illegal gambling operations — which led to the sweeping 2022 bust that netted Rosario and eight alleged mobsters

The Bonannos and Genoveses had originally agreed to split the take from the Gran Caffe, federal prosecutors said.

But the shaky peace eventually collapsed, and Rosario allegedly “sold himself” to the Bonannos, then staged fake police raids against rival gangsters.

“He chose the crime family over the public he swore to protect,” Anna Karamigios, assistant US attorney for the Eastern District, told jurors.

The Bonannos allegedly added Rosario to the family payroll and told him to hit Rubino’s spot around 2013.

Late Thursday, Sal the Shoemaker testified about Rosario’s spring 2013 faux-raid on his now-shuttered store.

He had been outside smoking a cigarette that day when Rosario and two others rolled up wearing police jackets and badges that hung from their necks, he said.

“He pointed at me to open the door and showed his badge,” Rubino told the court. “As soon as I opened the door, he started pushing towards the back — all three of them … asking, ‘Who’s in charge?’”

They asked about another Genovese associate, then busted the place up after Rubino said he wasn’t there — with one of the raiders shattering a gambling machine’s screen with the butt of his flashlight.

“They break-a the machine, and they said stay away from [the Genovese associate] and they left.”

“I went after them,” he continued. “I was like, ‘What’s going on? Why they break the machine?’ I don’t know. Something was not right.”

Then 60-year-old from Sicily — who once ran three illegal gambling spots in Long Island — fingered Rosario as the guilty party.

Rubino also said he vaguely knew Rosario, having seen him a few times before the raid and a week after at a shady club called The Blue Tequila, which was owned by mobster Sal Russo.

“He was just [hanging out] with Sal and the security guard there in the front of the place,” Rubino said.