A slight blast from the past as I'm catching up on trip reporting (although it doesn't really matter as the breakfast menu rarely changes significantly); here is the breakfast menu in LHR T5 Galleries First from May 2019.
You can read the full report here:
Hanoi and Hong Kong via QR and KA J featuring a Presidential Suite and CX F lounges
Both the smoked salmon and scrambled egg, and the Egg Benedict were edible although ultimately low quality (as is the norm). The scrambled egg is definitely from a packet and not freshly made.