National Kouign Amann Day is observed worldwide every June 20, celebrating the kouign amann, a Breton cake known for being “the fattiest pastry in all of Europe.” Originating in the commune of Douarnenez in Brittany around 1860, kouign amann is made from yeast-leavened dough layered with butter and sugar, resulting in a crispy exterior and soft interior. The holiday was established in 2015 by b. Patisserie, a bakery in San Francisco, to commemorate its opening day. To celebrate, people often purchase kouign amann from local bakeries or attempt to bake it themselves, sharing their experiences on social media with the hashtag #NationalKouignAmannDay. The pastry can be served as a large cake or in individual cupcake-sized portions known as kouignettes.