Place potatoes in a steamer basket in a pan with water. Water shouldn't be higher than the base of the steamer. Cover. Bring to a boil; reduce heat and steam the potatoes until they are tender, 20 to 25 minutes. Remove from heat.

Melt butter in a large skillet over medium heat. Add leeks; cook and stir until tender and translucent, about 7 minutes. Add parsley and seasoned salt, stirring to combine. Remove skillet from heat.

Gently stir in warm potatoes; season with freshly ground black pepper.