Sauté the Aromatics: Heat the olive oil in a large, deep skillet over medium-high heat until shimmering. Add the diced onions and cook, stirring frequently, until softened, about 5 minutes. Stir in the minced garlic and cook for another minute, being careful not to burn it. Transfer the sautéed aromatics to your slow cooker.

Brown the Beef: *In the same skillet, add the minced beef and cook over medium-high heat until evenly browned, about 8 minutes. Drain any excess fat. Transfer the browned beef to the slow cooker with the onions and garlic.

Make the Chilli: To the slow cooker, add the chopped tomatoes, green chillies, tomato sauce, chilli powder, paprika, ground cumin, ground coriander, ground cinnamon, salt, and black pepper. Stir everything together until well combined. Cover and cook on low heat for 5 to 6 hours.

Add the Beans: After the initial cooking time, add the drained and rinsed kidney beans and black beans to the slow cooker. Stir to combine. If the chilli is too thick, you can add a little water to achieve your desired consistency. Cover and continue to cook on low heat for an additional 5 to 6 hours.