Burger chain Shake Shack sizzles in market debut

- Shares of trendy hamburger chain Shake Shack Inc (SHAK.N) soared as much as 150 percent in their first day of trading on Friday, valuing a company with only 63 restaurants at nearly $2 billion. <br /> <br />The sizzling debut follows the successful listing two months ago of Habit Restaurants Inc (HABT.O), highlighting strong appetite for shares of companies serving up premium burgers. Other hot fast-casual restaurant debuts have been followed by stock swoons, including Noodles & Co (NDLS.O) and sandwich maker Potbelly Corp (PBPB.O). <br /> <br />Shake Shack shares were $48.31 in afternoon trade on the New York Stock Exchange, soaring above their offer price of $21 and raising questions about whether the stock was overvalued. Earlier in trading the shares hit a high of $52.50.