Everything has a LD50. Dodgy science based on tests with rats puts it at 1,000 mg/kg of body weight for theobromine, which is what would kill you in this scenario, and there’s between 2 and 6mg per gram depending on how nice your chocolate is. So for a 70kmg human that’s be maybe … 1.75kg? That seems low, I think I made an error somewhere.
Now I just need to find out what an Al Frankin is.