Heat bacon grease in a large pot over medium heat. Cook and stir pork in hot grease until evenly browned. Remove pork and liquid from the pot; set aside.

Melt butter in the same pot over medium heat. Sauté onions in hot butter until tender and lightly browned. Mix in paprika and flour; cook and stir until thickened.

Add pork, bell peppers, and jalapeño peppers to the pot. Stir in stock, tomato paste, garlic, salt, and bay leaf; bring to a boil. Reduce heat, cover, and simmer for 1 to 1 1/2 hours, stirring occasionally.