Serves six to eight.
- 3½ pounds russet potatoes, peeled and cut into ¾" cubes
- ½ tsp baking soda
- 3 T unsalted butter
- Kosher salt and pepper
- Pinch cayenne
- 3 T vegetable oil, divided
- 2 onions, cut into ½" dice
- 3 T minced chives
Adjust oven rack to lowest position, place rimmed baking sheet on rack, and heat oven to 500º.
Bring 10 cups of water to boil. Add potatoes and baking soda; return to boil, and cook for 1 minute (←not a typo). Drain potatoes, return to pot and cook over low heat, shaking pot occasionally, until surface moisture has evaporated, about 2 minutes. Remove from heat and add butter, 1½ tsp salt, and cayenne; mix with rubber spatula until potatoes are coated with a thick, starchy paste, about 30 seconds.
Remove baking sheet from oven and drizzle with 2 T oil. Spread potatoes on baking sheet in an even layer. Roast for 15 minutes. Meanwhile, combine onions, 1 T oil, and ½ tsp salt.
Remove baking sheet from oven. Using metal spatula, turn potatoes and clear an 8x5" space in center of baking sheet and add onions. Roast for 15 minutes.
Turn potatoes again, mixing with onions as you do so. Continue to roast until potatoes are well browned and onions are softening and starting to brown, 5–10 minutes. Stir in chives, and salt and pepper to taste, serve immediately.
Source: Cook's Illustrated January & February 2012