Smoked Trout Hash

Name: Smoked Trout Hash
Ingredients: 4 Tbsp. unsalted butter, divided; 1 lb. boiled and cooled russet potatoes, cut into 1/2″ cubes (2¼ cups); 1 small yellow onion, finely chopped (1½ cups); 1⁄4 lb. boneless smoked trout, flaked into large chunks; 1⁄4 cup heavy cream; 1 Tbsp. finely chopped fresh dill, plus more for garnish; 1⁄4 tsp. cayenne pepper; 1 medium garlic clove, finely chopped (1 tsp.); Kosher salt and freshly ground black pepper; 3 Tbsp. crème fraîche; 2 tsp. prepared horseradish; Finely chopped fresh chives, for garnish; Lemon wedges, to serve