since you asked:
it depends on what the two pieces did to your BG, testing would tell you and with that information you would be able to decide for yourself.
I can't say I carve anything so guilt does not come in to it. I know what I can and can't eat and, at the moment, stick to it.
"The odd one won't hurt", guess work or hoping so....
I make my own chocolates and know what is in them exactly and how many I can have at any one time... the answer is 2 and I limit myself to 1 as they are that good.