Heat oil. Saute onion until clear. Stir in curry powder, garlic, and mustard. Saute briefly. Add tomatoes, salsa, horseradish and vinegar. Simmer 1 hour, until thick. Squeeze moisture out of tofu and crumble into sauce. Simmer 30 mins more, until tofu absorbs flavor and tofu is of desired consistency. Season with salt and extra vinegar if desired. Serve in taco shells, garnished with yogurt, lettuce, tomatoes, cheese, salsa, etc.