Heat the vegetable oil in a large skillet over medium-high heat until it shimmers. Working in batches if needed to avoid crowding, add the beef stew meat cubes and sear them for 3-5 minutes, stirring occasionally, until they develop a golden-brown crust on most sides—this browning creates deep, savory flavors that will carry through the entire chili. Once browned, sprinkle the chili powder and ground cumin directly over the meat, stir well, and cook for 1 minute to toast the spices and release their aromatic oils. This toasting step is crucial; it transforms raw spice powder into a fragrant, flavorful base.

Dust the all-purpose flour over the spiced beef and stir constantly for 1 minute, coating all the meat pieces evenly. The flour will slightly stick to the hot meat and spices, creating a light roux that will help thicken the chili and create a rich, cohesive sauce. Transfer the entire contents of the skillet, including all the browned bits and spice coating, to your slow cooker—don't leave anything behind, as those browned bits contain concentrated flavor.

Add the diced onion, bell pepper, and minced garlic to the slow cooker and stir well to distribute them evenly among the meat. Pour in the diced tomatoes (with their juices), the drained kidney beans and black beans, the beef broth, barbecue sauce, brown sugar, and salt. The brown sugar balances the heat and acidity of the chili powder and tomatoes, while the barbecue sauce adds subtle smokiness and depth. Stir everything together until well combined, making sure the beef is submerged in the liquid.

Cover the slow cooker and set it to Low heat. Cook for 6-8 hours until the beef is fork-tender and falling apart—the long, gentle cooking allows the meat to break down completely and all the flavors to meld together beautifully. I prefer cooking on Low rather than High because it keeps the beans from breaking apart and gives the flavors more time to develop and deepen. You can check the chili after 6 hours; if the beef is already very tender, you can serve it, or let it go the full 8 hours for even more tender meat and concentrated flavor.

Once the beef is tender, taste the chili and adjust the seasoning if needed. If the chili seems too thick (which can happen as it simmers), stir in the remaining beef broth a little at a time until you reach your desired consistency—some people like it thick and hearty, while others prefer it more soup-like. Ladle the chili into bowls and top with fresh chopped parsley for a bright, herbaceous garnish that provides a nice textural and flavor contrast to the rich, slow-cooked chili.