'Wonka' Director Jokes About Chocolate Eaten on Set: 'It's a Miracle Timmy Remains So Slim' (Exclusive)

Wonka had quite the sweet film set.

The movie's director and co-writer, Paul King, reveals to PEOPLE that they had their very own on-set chocolate maker!

"I think I've [gained] about 50 pounds, but I hope I can lose it before [the movie] comes out," jokes King, 44, sharing that he was part of the lucky group of taste-testers.

As for star Timothée Chalamet, who plays the famous fictional titular chocolatier?

"It's a miracle that Timmy remains so slim and handsome," King quips. "I'm trying to fatten him up, but it's hard to do."

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Asked just how much chocolate the cast and crew consumed on set, King says it was a "great deal, which was a wonderful thing" that reminded him that his "life had taken a wonderful turn."

"We had this incredible chocolatier," he says. "She made these incredible concoctions, and we would taste them. They tasted much better than they needed to, because obviously actors are good at pretending things, but the miracle was they tasted every bit as good as they looked."

One especially sweet moment in the film involves Chalamet's Willy Wonka and his friend Noodle, played by Calah Lane, "in this huge vat of chocolate."

"We actually made an enormous vat of hot chocolate — not scalding, just warm hot chocolate for them to immerse themselves in," King says. "So there was there a lot of chocolate around."

On Tuesday, PEOPLE shared exclusive photos from the upcoming film along with more from the interview with King, in which he praised Chalamet as a "phenomenal actor" who was able to successfully put his own spin on the iconic character of Willy Wonka.

"I think what's so remarkable about his performance is not only that he is funny and mischievous and quite mysterious, as well — just like the Willy Wonka that people will know — but also, he brings such heart to the role and he's a brilliant actor," the director said. "He's incredibly emotionally intelligent and can bring a great deal of emotional truth to the role."

Additionally, King noted that fans of Chalamet might be surprised that he "can also sing and dance brilliantly," on top of his acting chops.

"It's really a tour de force for him there," he said of Chalamet's performance, adding, "He was rehearsing for months before we went to kind of that honing skills, which was a pleasure to watch."

Wonka floats into theaters Dec. 15.