I seem to recall reading somewhere that's how they make them - the 'white' and 'yolk' are solid, injected with an enzyme that will break them down into liquid(ish) then covered in the chocolate shell before they soften up.
Unsure how accurate this is, but it would explain your egg if it missed out on the enzyme part.
Internal-Special5739 t1_ja6xgxj wrote
Reply to My mom's Cadbury Egg is completely solid by DamnImCam
I seem to recall reading somewhere that's how they make them - the 'white' and 'yolk' are solid, injected with an enzyme that will break them down into liquid(ish) then covered in the chocolate shell before they soften up.
Unsure how accurate this is, but it would explain your egg if it missed out on the enzyme part.