The owner of the now-shuttered Grace restaurant is accusing top chef Curtis Duffy and general manager Michael Muser of making “extra profits by improperly using high-end ingredients provided by Grace at private events worldwide.”

Investor Michael Olszewski leveled the charge in a court filing Tuesday, escalating the bitter legal dispute with his former star employees at the widely renowned restaurant in the West Loop.

Grace was one of only two restaurants in Chicago with three stars in the prestigious Michelin Guide when it stopped operating abruptly in December, after Olszewski fired Muser and Duffy then quit.

Duffy and Muser had signed contracts with Olszewski in 2012 that prohibit them from opening a new restaurant in the Chicago area for 18 months from the time their work for Grace ended.

But Duffy and Muser sued the restaurant recently to have those non-compete clauses declared “unenforceable,” arguing that Grace is now closed.

In the new filing in Cook County Circuit Court, Olszewski said he plans to reopen Grace, at 652 W. Randolph St., on a daily basis “in the near future.”

And Olszewski said he had proof that Duffy worked at events in New York, Hong Kong, Florida and California “using food purchased with Grace’s accounts and shipped to various locations without my consent or approval.”

Olszewski said the restaurant ordered far more Wagyu beef than it was serving to customers at one point last year. The exhibits attached to his new court filing include shipping invoices showing Grace paid for ingredients sent across the country and as far as Asia.

After Duffy quit Grace, Olszewski said, “I discovered that $10,000 worth of truffles and a significant amount of produce was missing from Grace’s inventory. A portion of Grace’s wine inventory and Wagyu beef was also unaccounted for.”

Olszewski also alleged that “unexcused absenteeism became a chronic issue” with Duffy and Muser.

Sean O’Callaghan, the lawyer for Duffy and Muser, declined to comment Tuesday. A spokeswoman for Olszewski also declined to comment.

Olszewski is a real estate developer who was new to the restaurant business when he decided to invest in Grace and hired Duffy and Muser to work there.

Olszewski says the non-compete clauses were “the single most important parts” of his deals with Duffy and Muser, according to court records.

“If Duffy and Muser had not agreed to the non-compete clauses, I would never have moved forward with opening Grace and would never have made a $2.7 million investment in Grace,” Olszewski said.

The clauses keep Duffy and Muser from investing in a restaurant or even working for another place in Cook, Lake, Will, Kendall, DuPage, Kane or McHenry Counties, the Chicago Sun-Times has previously reported.

Olszewski says that a media interview with Duffy days after he quit Grace showed his intent to open a new restaurant and “steal Grace’s clientele.”

The “mutiny against Grace,” he said, caused him to shut the restaurant’s doors. Now, though, Olszewski said he has interviewed “several world-renowned chefs” from Greece, France, New York and Norway in his quest to replace Duffy.

“Closing Grace has never been considered as an option by me,” Olszewski said in his court affidavit.