Sarah Bern's try had been cancelled out by Valentina Ruzza who bulldozed over from close range.
But after the interval, the Red Roses clicked into gear and crossed for five more tries - including a treble for No.8 Hunter.
The game started perfectly for England, Bern emerging with the ball as the try scorer after a fine rolling maul inside five minutes.
But England were a little rusty in their first outing of 2018 and ill discipline allowed Italy back into it and it was Ruzza who got their deserved score just after the half-hour mark.
Michela Sillari added the extras and the two sides went in level at the break.
But a Katy Daley-McLean penalty on the resumption took the World Cup runners-up back in front.
And thereafter it was largely one-way traffic - Hunter the scorer from a lineout down the right although the extras went wide and it was 15-7 to the visitors.
A third try arrived almost immediately afterwards as the Italian defence began to look stretched, Poppy Cleall the beneficiary to dive over in the right corner.
Next to score was Abigail Dow, again in the right corner, but Daley-McLean was having an evening to forget from the kicking tee.
The fifth try was Hunter's second, and this time the fly-half added the extras and there was still time late on for full-back Ellie Kildunne to slide over.
And then with the final play of the game, after it looked like Hunter had missed her chance of a hat-trick, the England scrum demolished Italy on their own feed and Hunter dived on the loose ball for her hat-trick.