Shiffrin was tied with Vreni Schneider on 55 wins before her latest triumph.
And World Cup win number 56 came 24 hours after she and Petra Vlhova tied for first in the giant slalom.
This time, the American all but settled proceedings with a superb first run as she closes in on a third consecutive World Cup overall title.
Shiffrin resumes slalom reign
Shiffrin and Vlhova had filled the first two places in the first six World Cup slaloms of the season.
Shiffrin won the first five - taking her unbeaten record to seven - with Vlhova the runner-up each time.
Then the Slovak ended the win streak in Flachau, Austria, last month with Shiffrin having to settle for second.
But the double Olympic champion scorched down the first run a full second quicker than Vlhova in Slovenia.
Sweden's Anna Swenn Larsson was just nine-hundredths of a second further back with her team-mate, Olympic champion Frida Hansdotter, 1.57 seconds off the pace in fourth.
Hansdotter lost her place to Switzerland's Wendy Holdener with Swenn Larsson moving into the lead to secure her first podium finish since March 2014 and her second in all.
But then Vlhova had a disappointing descent, making several mistakes as she slipped down to fourth place.
Shiffrin led Swenn Larsson by 1.09 seconds from the first run and, despite losing some time in the middle of the course, had more than enough in hand.
She won by 0.77 seconds to extend her lead in the World Cup slalom standings.
More records in sight
Shiffrin is closing in on another record held by three-time Olympic gold medallist Schneider.
The Swiss secured 14 World Cup wins in the 1989 season as well as taking giant slalom gold at the World Championships in Vail, Colorado.
Saturday's victory was Shiffrin's 13th of the campaign in the last World Cup event before this month's World Championships in Are, Sweden.
Shiffrin told Eurosport afterwards, "This year has been very special. It's always a big fight but I'm really proud of this whole season. My team has done a great job and here we are."
Only Annemarie Moser-Proell (62) and Lindsey Vonn (82) sit above Shiffrin in the ladies' all-time World Cup list with two men - Marcel Hirscher (68) and Ingemar Stenmark (86) - also boasting more career wins.
On Friday, Vonn announced that she would be retiring from competitive skiing after the upcoming World Championships.
The 23-year-old goes to Sweden on top of the World Cup standings in slalom, giant slalom and super-G.
She starts her campaign in Are in the super-G on Tuesday (5th February).