Heat the olive oil in a large Dutch oven or pot over medium-high heat. Add the onion and cook, stirring, until softened, about 5 minutes. Add the bell pepper, jalapeno, garlic, five-spice powder and chili powder and cook for 3 minutes. Stir in the squash pieces, chicken pieces, tomatoes, beer, cocoa powder and brown sugar. Bring the mixture to a boil, stirring, then reduce the heat and simmer for 20 minutes.
Stir in the pinto beans and lime juice and cook for 5 minutes. Let the stew cool slightly, then ladle into bowls and top each serving with some cilantro, a dollop of sour cream and a lime wedge.