Heat oil in a frying pan over medium-high heat. Add onion, garlic and celery.
Cook, stirring, for 4 minutes or until onion has softened. Add capsicum and chilli powder.
Cook, stirring, for 1 minute or until fragrant. Transfer mixture to the bowl of a 5 litre slow-cooker.
Add tomato, stock, ham and 2 cups cold water. Cover. Turn slow-cooker on low. Cook for 6 hours or until ham is falling off the bone.
Remove ham. Remove and discard bones and rind. Using 2 forks, shred ham.
Return ham to soup with beans. Season with pepper. Cook, covered, for 30 minutes or until beans are heated through.
Meanwhile, preheat oven to 220°C/ 200°C fan-forced. Line a baking tray with baking paper. Cut tortillas into 3cm pieces.
Place on prepared tray. Bake for 5 minutes or until lightly browned and crisp.
Serve soup with sour cream and tortillas.