Original: Returning to the continent he followed the invitation of Tsar Alexander I to come to St. Petersburg , where he lived so briefly he never prepared a meal for the Tsar before returning to Paris , where he was chef to banker James Mayer Rothschild .
Simplified: He returned to Europe to work for Tsar Alexander I in St. Petersburg , before returning to Paris , where he was chef to banker James Mayer Rothschild .