Welcome to Discuss Cooking!
Let´s first address the problem of "eggs" and "salmonella". These days, most commercial eggs come from chickens that have been vaccinated against salmonella. Additionally, from what I´ve read, commercial eggs are often pasteurised, which kills off any bacteria.Most of the cases come from people who have chickens in their back yards. In 2019, 1,134 people went down with salmonella - in a population of 328,300,000. My suggestion is to make sure your eggs are (a) fresh (b) bought from a reliable source.
As for the chocolate mousse, I´ve never used a Hershey´s mix, but given the availability of excellent bean-to-bar chocolate these days, I´d avoid a ready made mixture and use the real thing.
This recipe comes from Jacques Pépin, an extremely accomplished chef .https://www.food.com/recipe/mousse-a...e-mousse-82175
Give it a go - it´s divine!