Heat the oil in a large heavy bottom saucepan over medium heat. Add the onions and cook until translucent but not browned, about 8 minutes. Add the garlic and cook 2 more minutes.
Reduce heat to low; stir in pumpkin puree, chicken stock and cooking sauce. Stir to combine and simmer over low heat for about 15 minutes, stirring occasionally.
Rough-chop the chocolate and add, stirring constantly, until it melts. Be sure to scrape the bottom of the pot while stirring. Cook for another 15 minutes, stirring occasionally.
Pour the cream into a bowl and add 1/4 cup of the hot soup, stir to combine, repeat, then stir it all back into the soup. Cook on very low heat until soup is hot, about 10 more minutes, stirring every few minutes. Adjust seasonings to taste.
Serve with a dollop of crema or sour cream as a garnish.