The correct Active/Passive form of the given sentence is:

☀ You are to write an essay.

Explanation for other options:

☀ You have to written an essay. This option is not grammatically correct. The correct form should be "You have to write an essay," not "You have to written an essay."

☀ You have to writing an essay. This option is not grammatically correct. The correct form should be "You have to write an essay," not "You have to writing an essay."

☀ You have had to written an essay. This option is not grammatically correct. The correct form should be "You have had to write an essay," not "You have had to written an essay."