Fresh Corn Spoon Bread

Name: Fresh Corn Spoon Bread
Ingredients: 1/2 medium yellow onion, finely diced; 1 stick unsalted butter (4 ounces or 1/2 cup); Salt; 2 cups whole milk (you can also use 2% if you prefer); 2 cups buttermilk; 1 3/4 cups finely ground white or yellow cornmeal; 1 tablespoon sugar; 1/4 teaspoon ground mace or freshly grated nutmeg; 1/4 teaspoon ground pink peppercorns; 2 to 3 teaspoons finely chopped fresh marjoram or thyme (or both) (optional); Butter or oil for greasing the dish; 5 large eggs, separated; 1 1/2 cups corn kernels, preferably raw; Freshly ground black pepper