Bill Ackman’s two-year bet on Burger King Worldwide Inc. is paying off in a big way as the fast-food chain soared in trading Monday.

Pershing Square Capital Management LP’s 10.9 percent stake in Burger King increased in value today by $171 million to about $1.2 billion, according to data compiled by Bloomberg. Ackman helped Burger King go public in 2012 after it merged with Justice Holdings Ltd., a special-purpose acquisition company co- founded by the hedge-fund manager. The stock has more than doubled since September 2012 when Ackman disclosed Pershing Square’s stake.

Burger King rose 16 percent to $31.55 at 10:49 a.m. in New York. after disclosing that it’s in talks to buy Tim Hortons Inc. and move its headquarters to Canada. This would create the world’s third largest fast-food chain and lower Burger King’s tax rate.

Pershing Square, which oversees $15 billion, has gained 26 percent this year through July in its main hedge fund, profiting from investments including Fannie Mae and Freddie Mac shares, and on its bet against Herbalife Ltd.

Francis McGill, a spokesman for Pershing Square at Rubenstein Associates Inc., had no immediate comment.