In a ~5 quart heavy-bottom soup pot, heat 2 tablespoons of olive oil and sauté the diced onion in the olive oil for 5 minutes over medium heat.
Add the rest of the olive oil (2 tablespoons) and cook the ground beef over high heat for about 5 minutes or until it is browned, using a spatula to break up the beef.
Add the next 12 ingredients (diced tomatoes through raisins) and mix well. Cover and bring to a boil. Crack open the lid and lower the heat to a simmer. Simmer for 20 minutes, or until the sweet potatoes are fully cooked and the chili has thickened to your liking. Season with salt and pepper to taste. For some extra heat add another 1/4 teaspoon cayenne pepper.
Let stand 5 minutes before serving. Top with sour cream, shredded cheese, cilantro, or your favorite chili garnish. Serve with crackers or crusty bread to dip into the chili.