Correct spelling, explanation: this is the correct spelling, because of its origin; chocolate comes from Aztecan word(s) meaning chocolate bean and water, chocola-tl, where the o is present as well. That’s why chocolate is the correct form and choclate is incorrect (despite the pronunciation).

Definition of chocolate:
noun, type of food made of cocoa beans
Mary doesn’t drink coffee but is addicted to hot chocolate.
There is nothing better than a chocolate bar with a cup of tea!

Incorrect spelling, explanation: choclate is a mistake because there should be an o in the spelling (chocolate), just as in Nahuati (Aztecan) roots: chocola-tl. The mistake is probably made due to pronunciation, however, the correct form is chocolate.