Mashed Potatoes and Leeks

12 baking potatoes
4 large leeks
2 tablespoons unsalted butter plus 1/2 cup
2 cups chicken broth
Salt and white pepper
1 cup sour cream
1/2 cup whole milk

1. Peel potatoes and quarter them. Put in a pot of cold water with some salt and bring to a boil. Turn down to a simmer and cook until tender, 15 to 20 minutes.
2. Clean and chop leeks. Melt the 2 tablespoons butter in a large saute pan. Add leeks and sweat until they are soft and translucent. Add chicken broth and a little salt and white pepper and simmer for 3 to 4 minutes. Puree all in blender and put aside.
3. Mash the potatoes with a masher. Add leeks, sour cream, 1/2 cup butter, and milk. Whip with an electric hand mixer. Do not over beat. Season, to taste, with salt and white pepper. Can be reheated in microwave before serving.