Was much of the text actually written by him, or was it instead mostly written by his administrators? I know there have been a few Napoleon posts today, but those are what made me wonder about this so I figured I'd ask anyway.
After the Second Italian campaign. Napoleon asked Cambacérès(The Second Consul ) to lead the commission who was created by consular judgment in 18 August 1800. With the help of Two lawyers Bigot de Préameneu and François Denis Tronchet and the help of two jurists Jacques de Maleville and Jean-Étienne-Marie Portalis . They wrote the articles in four months. Maleville used to sleep only 5 hours per day.
After that the Supreme Court of France and the Assembly did a review with Napoleon Bonaparte. They did only minor changes.
Tl;dr:The Napoleonic code was written by Cambacéres with the help of two lawyers and two jurists.
Source: Robert B. Holtman, The Napoleonic Revolution