Spinach Spoon Bread

Name: Spinach Spoon Bread
Ingredients: 3 tbsp. unsalted butter; 10 oz. baby spinach; 3 c. buttermilk; 3 large eggs; 1 c. medium-grind yellow cornmeal; ¼ c. all-purpose flour; 1 tbsp. sugar; 1½ tsp. baking soda; 1 tsp. kosher salt; 1 pinch freshly grated nutmeg; 1 pinch freshly ground white pepper