Boerenkool Stamppot (Kale and Potatoes)

2 lbs. yellow potatoes
1/2 yellow onion
5 cloves garlic
2 tbsp butter
2 tbsp sour cream
1 lb. fresh kale
salt and pepper to taste

Dice potatoes and onion and toss into a pot. Cover with water, and cook over low heat for 5 minutes. Mince garlic, and add to pot. Cook for 10 minutes.
Meanwhile, finely chop kale, and place in a separate pot, with about a 1/4 cup of water. Cook for about 10 minutes, or until wilted.
Drain water from potatoes. Mash with potato masher, until relatively smooth. Add butter and sour cream, and stir until melted. Toss potatoes with kale. Season with salt and pepper.