Heat oil in a large Dutch oven over medium-high; sear brisket well on all sides in batches, about 10 minutes total. Set aside.
Brown pork in same pot about 6 minutes, breaking up with a spoon; add onions and cook about 5 minutes until soft.
Cook garlic 1 minute; stir in chili powder, cumin, paprika, oregano, cinnamon, and cloves. Cook 1 minute until fragrant.
Return brisket; stir in tomatoes, broth, beer, paste, cocoa, salt, pepper, and bay leaves.
Boil; reduce heat to lowest setting, cover with lid slightly ajar, and simmer 10 hours overnight, checking once or twice if possible.
In morning, discard bay leaves; skim surface fat if desired.
Adjust seasoning; simmer uncovered 30 more minutes for thicker chili, or serve immediately with preferred toppings.