How to Make It
Preheat oven to 450ºF. Microwave 1/2 cup of the butter in a microwavable bowl on HIGH until melted, about 30 seconds. Toss together potatoes and melted butter in a large bowl. Transfer to a large, rimmed baking sheet, spreading potatoes in a single layer; pour any remaining butter in the bowl over potatoes. Sprinkle with 1/2 teaspoon of the salt and 1/4 teaspoon of the pepper. Roast potatoes in preheated oven until bottoms are lightly golden, about 15 minutes. Flip potatoes, sprinkle with 1/2 teaspoon of the salt and remaining 1/4 teaspoon pepper. Return to oven, and bake until potatoes are very brown, about 10 minutes. Add stock to baking sheet, and bake at 450°F until most of the liquid has evaporated, about 10 minutes.
Meanwhile, combine walnuts, syrup, and remaining 1/4 cup butter and 1/2 teaspoon salt in a saucepan over medium. Bring to a simmer, stirring to emulsify butter and syrup. Remove from heat.
Transfer potatoes to a platter. Drizzle with syrup mixture just before serving.