Shake Shack, the fast-food restaurant chain that has developed a cult following for its ‘Shackburgers’, ‘flat-top’ hot dogs and eponymous shakes, has selected JPMorgan Chase & Co (JPM.N) and Morgan Stanley (MS.N) to lead a proposed initial public offering, according to people familiar with the matter. The potential offering, which could come as soon as this year according to the people, would be the biggest public event for a company that started out of a hot dog kiosk in New York’s Madison Square Park in 2004.