In a large pot or Dutch oven, cook the chopped bacon over medium heat until crispy. Remove bacon and set aside, leaving the bacon fat in the pot.
Add the steak pieces to the pot and brown on all sides in the bacon fat, about 5-7 minutes. Remove steak and set aside.
Lower the heat to medium-low, then add tomato paste, stirring into the bacon fat to cook briefly, about 1-2 minutes.
Add chili powder, ground cumin, black pepper, and cocoa powder to the pot, stirring to combine and let spices bloom, about 1 minute.
Pour in tomato sauce and stir well, scraping any browned bits from the bottom of the pot.
Return the steak and bacon to the pot, then add kidney beans. Stir to combine everything evenly.
Simmer the chili gently over low heat, partially covered, for about 45 minutes to allow flavors to meld and steak to tenderize.
Taste and adjust seasoning with salt and more pepper if desired before serving hot.