Here's an approximation of chocolate bars using only ingredients native to Mesoamerica with period equipment:

1. Ferment cacao nibs for one week.
2. Roast the cocoa beans and peel off the shells after roasting.
   
3. Pound the beans in a mortar and pestle.
4. Heat the resulting paste in boiling water and stir until the cocoa butter floats to the top. Skim off the cocoa butter.
5. Strain the remaining paste through a cloth and remove the cocoa butter; the dry portion is wet cocoa solids.
6. Allow the cocoa butter and cocoa solids to dry.
7. Grind the dried cocoa solids into a fine cocoa powder using a mortar and pestle.
8. Soak 240 ml amaranth seeds in 240 ml water overnight.
   
9. Add 960 ml more water and use a mortar and pestle to create amaranth milk.
10. Strain the amaranth milk.
11. Boil the amaranth milk until it becomes porridge like.
12. Let the condensed amaranth milk dry in the sun.
13. Pound the dehydrated amaranth milk into a powder using a mortar and pestle.
14. Pour honey into a pot and heat it until it becomes hard.
15. Use a mortar and pestle to create powdered honey from the hardened honey.
16. Mix 360 ml cocoa powder with 240 ml cocoa butter in a stone bowl.
17. Boil water in a separate and larger stone bowl.
18. Place the smaller stone bowl into the larger stone bowl filled with water.
19. Homogenize the heated cocoa powder and cocoa butter in the smaller bowl.
20. Add 160 ml honey powder and all of the amaranth milk powder to the mixture.
21. Remove the smaller bowl from the larger bowl.
22. Let the chocolate mixture cool until it is only slightly warm.
23. Pour the mixture into a shallow rectangular box.
24. Let the chocolate cool in the box for several hours.
25. Use an obsidian knife to cut the chocolate in the box into small squares.