Leek and Potato Soup, with Kale and a Turnip

My mom always made leek and potato soup and served it with salad and buttery toasted pita. It's such a great dinner for a cold day. I wanted to make the usual soup, but I also picked up a turnip and a bunch of kale to change it up a little. I ended up making way more soup than necessary, so I'll be eating it for days. All of the ingredients cost $10. It's really tasty, and the kale gives it a nice green color (and some extra healthiness). Serve it with some pita toasted with butter and a salad.

Ingredients:
5 medium-sized potatoes (any kind you want), peeled and chopped into 1" cubes
3 large leeks, rinsed and thinly sliced
1 turnip, peeled and cut into 1" cubes
2 tbsp butter
1 bunch kale, rinsed and ripped into pieces