4 tablespoons unsalted butter
1 cup finely chopped onion
4 cups water
3 cups peeled and diced Yukon Gold potatoes
1/2 teaspoon salt
2 1/2 tablespoon all-purpose flour
1 1/2 cups milk
1/2 teaspoon dried sage
1/2 teaspoon ground pepper
6 oz. grated sharp cheddar cheese
1. In large saucepan, melt 2 Tbs. butter over medium heat. Add onion, and cook, stirring often, until softened, 7 minutes.
2. In a large pot, boil the potatoes in water seasoned with salt till tender.
3. Meanwhile, in small saucepan, melt remaining 2 Tbs. butter over medium heat. ]
4. Stir in flour, and cook, stirring constantly, until sauce thickens slightly, about 5 minutes.
5. Whisk 1 cup of hot potato broth, a little at a time, into sauce.
6. Simmer another minute, and remove from heat.
7. Transfer cooked potatoes to a medium bowl and mash with a potato masher.
8. Once potatoes are mashed, stir back into broth along with sauce, milk, sage and black pepper to taste.
9. Bring soup just to a boil, stirring, then remove from heat.
10. Stir in cheese, a little at a time, until melted.
11. Taste soup, adjusting seasonings if necessary. Serve hot.