Place potatoes in a large saucepan; cover with water. Bring to a boil; reduce heat, and simmer 15 minutes or until tender. Drain; return potatoes to pan.
While potatoes cook, heat oil in a small saucepan over medium heat. Add mustard seeds; cook 2 minutes or until seeds begin to pop. Add milk, syrup, and turmeric; simmer until reduced to 1/2 cup (about 10 minutes). Add milk mixture, salt, and pepper, and mash with potato masher or fork to desired consistency. Serve immediately.