Substitute for egg yolk in chocolate truffles? I have a recipe for chocolate truffles (basically butter and chocolate) that also includes an egg yolk; presumably to help smooth it and increase the richness. 

I know that the recipe would probably work just omitting it, but,

Is there a non-perishable, and preferably vegetable based, substitution that could be used?
Classic French truffles often add an egg yolk for enrichment. You could use a pasteurized egg product if you'd like, or depending on the recipe you could leave it out all together or replace it with cream since you're using a butter ganache. Alternatively, you can stream in 1/4 cup of boiling water/cream per egg yolk very gently and while whisking to bring the yolks up to 160 degrees. This must be done slowly to prevent the eggs from scrambling.