In a large, heavy-bottomed pot over medium-high heat, sauté onion, bell pepper and celery until tender. Add garlic and sauté for 30 seconds.
Add bay leaf, thyme, cayenne pepper, hot sauce, salt, pepper and stock.
Bring to a boil, add beans, then reduce to a simmer.
Cook uncovered, stirring often, for 20 minutes. Remove bay leaf.
Transfer about 2 cups of the mixture into a bowl and mash well with a potato masher or hand blender.
Return mashed beans to the pot, taste and adjust seasoning, and simmer for 5 minutes longer, adding additional stock if bean mixture is too thick.
Serve beans over hot, cooked oats, sprinkle with chopped parsley and pass the hot sauce.