Heat the butter in a non stick pan, when melted and hot, add the onion, garlic, bell pepper, celery, and jalapeno pepper (if using) and cook and stir for a few minutes, you are not trying to brown them, just heating them all through, remove from heat and pour it all, butter and all, into your slow cooker, there, you just made a mirepoix :)
Drain and rinse the beans, add to the slow cooker, then add diced ham, sliced sausage, bay leaves, 1/2 teaspoon of Creole seasoning.
Here I added the mirepoix after I added beans, ham, and sausage. The order in which you add it does not matter at all.
Add the stock and 4 cups of water, add more water as needed to make sure everything is covered by the liquid, also take into account the beans will expand some during cooking so do not overfill the slow cooker. Stir to mix everything together.
Cover and set to Low setting and cook for 8 to 10 hours for the consistency of beans you prefer.
Remove the bay leaves, stir in the remaining Creole seasoning, serve over cooked rice.