Neil Harris hit his second hat-trick of the season as Millwall finally ended their awayday blues at the 13th attempt with an emphatic victory at Edgeley Park.
Chopper, who bagged a treble against AFC Bournemouth in the Carling Cup, struck after 24, 36 and 67 minutes - and could have finished with four goals if he had not seen his 39th-minute penalty saved by Owain Fon Williams.
Skipper Paul Robinson, back in the starting line up in a League game for the first time in 10 months, made it a perfect return as he opened the scoring on 16 minutes and then played his part as The Lions kept a clean sheet for the third time in four games.
Millwall boss Kenny Jackett was forced to change his defensive formation with Scott Barron joining Andy Frampton and James Henry on the sidelines after sustaining an injury in training on Friday.
Having failed to win on their travels since 31st March, Jackett made five changes in total from the team that started at Swindon last weekend in a bid to find that winning formula away from The Den.
Skipper Robinson took his place in central defence alongside Tony Craig,
Alan Dunne returned to the starting line-up at right-back, with Danny Schofield replacing Dave Martin on the left. Chris Hackett filled in for Henry on the right flank and Harris partnered Steve Morison in place of Gary Alexander.
Alexander was joined on the bench by teenage defender Omar Beckles, making the cut for the senior squad for the first time.
The game started a frantic pace with Greg Tansey's low drive flashing wide on two minutes and then Hackett sending his fifth minute effort straight into the hands of Owen Fon Williams in the home goal.
Morison went close seconds later, picking up Dunne's angled pass before sending a rasping 20-yard shot narrowly over.
Morison was inches away from connecting with Harris' sublime switch pass, and it was from his persistence that The Lions won a 16th-minute corner.
Hackett's first delivery was put behind for another corner and when he swung the ball over for a second time, there was Robinson to plant a firm header home for the opening goal.
Lions fans behind the goal were celebrating again just six minutes later when Harris showed great instinct to capitalise on a woeful misplaced header by Paul Huntington and clipped the ball past Fon Williams for goal number two.
County nearly reduced the arrears barely three minutes later from their first corner of the game when Johnny Mullins' header was somehow scooped off the line by David Forde. Peter Thompson's follow-up shot was then blocked in an almighty scramble before the danger was finally averted.
Craig then cleared off the line from David Poole's effort, but the referee blew for a foul on David Forde as County began to press.
However Millwall soon took the sting out of the situation in perfect fashion. Schofield did well to block a crossfield pass, the ball fell to Hackett and his perfectly weighted throughball picked out Harris in a central position. Chopper strode forward before despatching a clinical finish to make it 3-0 with 36 minutes on the clock.
Harris had a great chance to complete his hat-trick three minutes later when he was sent tumbling in the area by the hapless Huntington.
The striker picked himself up, but sent his powerful spot-kick too close to keeper Fon Williams, who got his body fully behind the ball to deny Chopper his hat-trick - and Millwall a fourth goal.
Stockport boss Gary Ablett not surprisingly made a couple of changes at the start of the second period, bringing on Danny Pilkington and Oli Johnson.
No doubt responding to some straight talking from their manager, County certainly had more purpose about their play in a bid to try and claw their way back.
Michael Rose saw his low drive held by Forde and Johnson flicked a header over and then sent another straight at Forde as the home side tried to build up a head of steam.
Hackett, Schofield and Harris combined to set up Millwall's first chance of the second-half after 65 minutes, only for Morison to glance his header a yard over.
Morison, enjoying his best game for The Lions, produced a delightful combination of power and skill two minutes later, working his way into the box before selflessly squaring to Harris, who poked over the line for his hat-trick.
It took a stunning save at full stretch by Fon Williams to divert Morison's piledriver for a corner and deny the striker the goal his display deserved.
Morison was eventually replaced by Gary Alexander five minutes from the end - the third and final substitution made by Jackett.
And it was Alexander who nearly made it five deep in injury-time with a stinging 20-yard drive that the overworked Fon Williams parried at full stretch.
A fifth goal would have been no more than The Lions deserved for a five-star team display.
Stockport County: Fon Williams, Mullins, Rose, Bridcutt, Raynes, Vincent (Pilkington, 46mins), Tansey (Johnson, 46mins), Baker, Poole (Griffin, 71mins, Thompson, Huntington. Subs not used: Turnbull, Gerrard, Halls, Havern.
Booking: Tansey (28mins)
Millwall: Forde, Dunne, Smith, Laird, Robinson, Craig, Schofield, Abdou (Bolder, 77mins), Harris (Price, 73mins), Morison (Alexander, 85mins), Hackett. Subs not used: Sullivan, Grabban, Martin, Beckles.
Scorers: Robinson (18mins), Harris (24, 36, 67mins)
Ref: Mark Haywood
Att: 4,394 (away 461)