In hot oil, sauté onions and garlic until onions are soft.
In sauce pan, add fresh mangoes, carrots, vinegar, lime juice, salt, and habaneros. Bring to a boil, then lower heat and simmer until carrots are soft. Transfer to a blender. The fumes can be tough on wives and pets, so consider doing out side.
Add onions, garlic, and puree until smooth.
Return to stove and simmer until desired consistency. If too thick, add vinegar.
Strain if you plan to put sauce in a typical hot sauce bottle with tiny opening, otherwise leave as is. Getting the sauce into the bottle can be tough. I found using a turkey injector works pretty good, if you have strained the sauce. If you do strain, save the "pulp" and add it to other recipes that call for fruit and heat. It freezes well.