Preheat a waffle iron according to the manufacturer's instructions. Preheat the oven to 200°F. Into a medium bowl, sift the flour, baking powder, and salt. In a large bowl, beat together the egg yolks and sugar until the sugar is dissolved and the eggs are a pale yellow color. Add the milk, melted butter, and vanilla extract and whisk to combine. Add the flour mixture to the egg mixture and whisk just until blended. Do not overmix.
In a third bowl, beat the egg whites until soft peaks form. Using a rubber spatula, gently fold the egg whites into the waffle batter, being careful not to overmix.
Coat the waffle iron with nonstick cooking spray as required and pour enough batter in the iron to just cover waffle grid. Cook according to the manufacturer's instructions until golden brown, 2 to 4 minutes, depending upon size. (In checking for doneness, open the waffle iron carefully and watch out for steam. Do not open the waffle iron for at least 1 minute.) Place the cooked waffles on a baking sheet and keep warm in the oven while cooking the remaining batter and preparing the remaining ingredients. (Note: Waffle batter makes 2 to 3 large waffles, or 8 to 10 small 4-inch waffles.)
Lightly grease the grill and preheat to medium-high heat. Place the ham steak on the grill and cook until lightly browned and slightly crisp around the edges, about 5 minutes per side.
To serve, place 1 large waffle on a large dinner plate and top with the grilled ham steak. Position 4 poached eggs on the ham steak, dividing it into quarters, and spoon the sausage-milk gravy over the ham and eggs. Garnish with chopped chives and serve immediately.
Makes 2 to 4 servings