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The 15-year-old clocked one minute 50.23 seconds over her two runs, 0.96 seconds ahead of Germany's Hannah Neise.
Pittaway's triumph follows fellow Brit Madi Rowlands, who won gold in the ski halfpipe on Sunday in Lillehammer.
Rowlands, 15, added a bronze in the women's ski slopestyle final on Friday.
"When I first crossed the line I couldn't believe it," said Pittaway.
"I felt like I was standing next to me watching me finish - it was so surreal and just like a movie.
"Hannah [Neise] is one of my best friends and we're really happy to be on the podium together. That's been our dream together for four years."
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Ashleigh Pittaway claimed Great Britain's second gold medal of the Winter Youth Olympics, winning the skeleton bob event in Norway.