"I developed this bison chili recipe together with my dad one afternoon when we realized we weren't thrilled with any of the chili recipes we had tried before. This is a sweet and sour recipe with a mild finish, so it's tasty for kids as well as adults. With all the beans and tomatoes, it's a pretty forgiving dish. This is a time-intensive recipe, but it yields a lot of food, so plan for leftovers. Serve with Greek yogurt on top or over a baked potato."
Place bacon in a large skillet and cook over medium-high heat, turning occasionally, until crispy, about 7 minutes. Drain bacon slices on paper towels; retain grease in the skillet.
Heat olive oil in a large pot over medium heat. Add ground buffalo and vinegar. Cook and stir until browned, 5 to 7 minutes. Add the bacon.
Put onions in the skillet with the reserved bacon grease. Cook patiently over medium-low heat until deeply browned, 20 to 30 minutes.
Stir crushed tomatoes, diced tomatoes, and garlic cloves into the pot with the buffalo and bacon. Add the browned onions, pinto beans, red pepper flakes, salt, sage, fennel seeds, and cumin. Stir regularly over low heat until flavors have combined, about 1 hour.