While each product featured is independently selected by our editors, we may include paid promotion. If you buy something through our links, we may earn commission. Read more about our Product Review Guidelines here. Fall has officially begun — at least according to Kourtney Kardashian’s hair. The reality star and Lemme founder kicked off what she calls “witchy season” in a moody mirror selfie on Instagram on Sept. 20, debuting a fresh set of one of this year’s most popular hair trends: “Birkin” bangs. The cut feels effortlessly cool and a little mysterious, giving her look an instant edge that feels perfect for this time of year. Named after ’60s…