I did something like this as a kid too…. With quality street. Every night I’d come in from school and carefully peel back the seal, eat a couple and put them back under the Christmas tree.
Christmas morning comes, mum opens the lid to a fairly lightweight tin and I prepare to confess. Only before I could she went into a rant about rowntree and under weight products. I kept my mouth shut.
She sent them a stink of a letter and got lots of vouchers as an apology.
I was in my forties before I came clean.