How to Make It
Preheat oven to 450°F.
To prepare the mashed potatoes, place potatoes and bay leaves in a large Dutch oven; fill with water to cover potatoes by 2 inches. Bring to a boil; reduce heat and simmer 25 minutes. Drain; discard bay leaves. Return potatoes to pan; mash to desired consistency. Stir in butter and 2 teaspoons salt. Reserve 8 cups mashed potatoes for Forager's Pie and Buttermilk Potato, Chicken, and Cheddar Casserole. Stir horseradish into remaining 3 cups mashed potatoes; keep warm.
To prepare the salmon, place a wire rack on a rimmed baking sheet; cover with foil and coat with cooking spray. Place fish, skin side down, on foil. Combine oil, thyme, mustard, curd, vinegar, and pepper in a bowl. Brush half of mustard mixture over fish. Bake in preheated oven 15 minutes. Brush fish with remaining mustard mixture; bake 7 minutes. Place fish on a platter; sprinkle with 1/2 teaspoon salt and dill. Serve with lemon wedges and mashed potatoes.