Preheat oven to 375 degrees Fahrenheit.

Heat butter in a large pot. Add onions and garlic, sprinke with salt and pepper, and sauté until translucent.

Add cubed potatoes, sweet potatoes, water, milk, sour cream, salt and pepper and bring to a boil. Cook for half an hour, until potatoes are soft. (Stir occasionally).

While the soup is cooking, roughly chop broccoli and spread on a lined pan. Place in oven and bake uncovered for 10 minutes, and then covered for another 10 minutes

Partially blend the soup with an immersion blender. Blend until thick but chunky.

Add broccoli to the soup and cook for an additional 15 minutes.

Place a handful of shredded cheese in a bowl and ladle the soup over it.