The former Kendal Town midfielder capitalised on some dodgy defending midway through the first half to take the points back along the A96 and maintain his side's hope of staying in contention for second spot in the SPFL table come May.
His opportunist strike midway through the first half left Hughes pleased that some hard work on the training pitch last week had brought its reward.
"I was concerned at the physical presence of Aberdeen, he said. "But we stood up to it and throughout the match some of our football was exceptional and all the best chances, I felt, fell to Inverness.
"What we've done on the training pitch was close the back door and we have the knowledge that with Billy McKay up front, we're always capable of getting something."
Russell Latapy, named last week as his assistant after a spell with the Portuguese club, Boavista, will start work on Tuesday. The former midfielder, who played under Hughes at Falkirk, has been in his native Trinidad on business but he will be a big asset to the Inverness cause, according his new boss.
"He's an astute and clever tactician who will be good for the club," explained Hughes. "He likes the game played in a certain way and our touch players will learn from him."
The return of Andrew Considine after a month sidelined through injury prompted Derek McInnes, the Aberdeen manager, to reshape his defence with Jonny Hayes - a makeshift left-back in his absence - left out to accommodate his colleague.
But Considine was left exposed early on as Aaron Doran found space on the right to feed McKay. The striker could not make a proper connection, however, and the opportunity came and went without success for the visitors.
Hughes may have been concerned by the difficulties his defenders faced in dealing with Barry Robson's wicked set-pieces, but a cross at the other end of the park in the 22nd minute would give the Inverness manager cause for celebration. Doran's delivery from the right was touched on by McKay and with Alan Tate and Russell Anderson posted absent, Williams raced into space and finished in style.
It marked the first of several occasions Williams was afforded space as Tate, signed on a loan deal from Swansea City two weeks ago and who prefers to operate at centre-back, looked uncomfortable at right-back.
Despite facing a strong second-half wind, Inverness produced the more attractive football as the hosts toiled to find a fluency to their play, which was perhaps why they replaced Robson and Tate with Hayes and Joe Shaughnessy, two more attacking participants, on the hour mark.
Certainly, their determination to find an equaliser couldn't be faulted and they came extremely close with 20 minutes remaining as Willo Flood hit a dipping strike from distance, only for Dean Brill, the visitors' keeper, to tip the effort over the bar.
Flood lost possession 10 minutes later to Graeme Shinnie, outstanding in midfield for the visitors and, after playing a give-and-go with McKay, his 25-yard struck Jamie Langfield's right-hand post.
Aberdeen's lack of invention continued to frustrate them, while a further defensive lapse allowed McKay in on goal, though his strike flew wide.
"I anticipated a tight match," McInnes said, "But full credit to Inverness who broke on us well and worked hard to nullify our passing game; we never really got going at all.
"We've been striving for consistency since the start of this season but our performance wasn't what we're capable of.
"I felt we were a bit too frantic for my liking, but we're still in second place in the league."
McInnes declined to discuss reports of his interest in strikers David Goodwillie and the former Inverness player, Adam Rooney, now at Oldham.