Crumble the mince into a large microwave-safe bowl. Cook for 3 minutes on high; drain fat and stir in onion, chilli powder, basil, 1/2 teaspoon garlic powder, tomatoes and tomato paste. Add the water. Cover bowl with cling wrap and microwave on high for 10 minutes.
Stir broken spaghetti into meat mixture; re-cover with cling wrap and microwave on high for 6 minutes. Stir, re-cover and microwave on high for 3 to 4 minutes, or until spaghetti is tender. Stir in beans, re-cover and let stand 5 minutes.
In a separate bowl, combine cheese, sour cream and remaining 1/4 teaspoon garlic powder. Microwave on medium-high for 2 minutes, or until cheese is melted. Serve over spaghetti mixture.