Preheat the oven to 425°F. Put a half-sheet pan in the oven (itll heat up while the oven preheats).

Add the potatoes to a pot with 1 tablespoon salt; cover with about 1 inch of water. Bring to a boil, reduce heat to low to maintain a simmer, and cook for 5 minutes, or until easily pierced with a paring knife, but the center is still hard.

Whisk together 1 1/2 teaspoons kosher salt, 2 tablespoons olive oil, mustard, and black pepper in a large mixing bowl.

Thoroughly drain the potatoes and then toss with the mustard mixture.

Take the preheated sheet pan out of the oven, drizzle with 1 teaspoon olive oil, and tilt the pan to spread it evenly. Add the potatoes, arranging them so that a flat side is in contact with the pan, and bake for 25 minutes, or until the bottoms are brown. Flip the potatoes and cook for another 15 to 20 minutes, or until deeply browned and tender.