Falkner graduated from the San Francisco Art Institute in 1989 with a BFA in fine arts. She began her career in 1990 as the chef at Cafe Claude, before moving to Masa's with Chef Julian Serrano. In 1993, Falkner became the pastry chef at Elka in the Miyako Hotel, and in 1994 Falkner was hand-picked by Chef Traci Des Jardins to head the pastry division at Drew Nieporent's Rubicon.
In 1997, Falkner opened Citizen Cake at its first location in the South of Market district of San Francisco. It remained there until 2000 when she moved the restaurant to 399 Grove Street, in the Hayes Valley district. From 2001 to 2002, Falkner taught professional pastry courses in Japan; and, from 2002 to 2003, she was a consultant on pasta for Barilla in Parma, Italy. In 2005, she began to expand her role at Citizen Cake from pastries into the lunch and dinner menus.
In 2006, Falkner appeared as a guest judge on Top Chef, a reality show on the Bravo network. She has also appeared on Iron Chef America, Tyler's Ultimate, $40 a Day, Sugar Rush, Best Of, Bay Cafe, Top Chef-Pastry and others. She has cooked at the James Beard House in New York, the Masters of Food and Wine in Carmel, CA, and the Chef's Holiday at the Ahwahnee Hotel in Yosemite National Park. In 2010, Falkner relocated Citizen Cake to 2125 Fillmore Street, and was rumored to be planning to launch a weekend brunch service at her other restaurant Orson. She is the runner-up of the fourth season of The Next Iron Chef, losing in the finale to Geoffrey Zakarian, and finished sixth in the fifth season, with a loss to Nate Appleman.