The Eggcorn Database - v. 0.5

As noted by Ken Lakritz, this is a common error. The search engines turn up hundreds of links to recipes.

It is not entirely clear whether we have a simple hesitation about the correct spelling of _bouillon_. But in this case, we might expect the form _boullion_, which is indeed just about as frequent as _bullion_. To bolster the eggcorn hypothesis we note that bouillon cubes come in an individual gold or silver wrapping at least in some parts of the world, and do slightly resemble miniature ingots.