dnd 5e – How does the Potent Cantrip-Sidekick Feature work with multiple Eldritch Blast-beams?

Let’s assume a sidekick with the prodigy role, CHA 20 and the potent cantrips-feature :

“The sidekick can add its spellcasting ability modifier to the damage it deals with any cantrip.”]

Could this Sidekick add the spellcasting ability modifier of +5 to each beam of an Eldritch Blast or does the sidekick have to choose a single of the beams that gets the additional damage?