In a small bowl, combine the lukewarm milk and granulated sugar. Sprinkle the yeast over the top and let it sit for about 5-10 minutes until it becomes frothy.
In a large mixing bowl, whisk together the all-purpose flour and kosher salt. Make a well in the center of the dry ingredients.
In another bowl, whisk the egg yolks and melted butter until combined. Pour the activated yeast mixture into this bowl and mix well.
Pour the wet mixture into the well of the dry ingredients. Mix until just combined; the batter will be thick.
In a separate bowl, beat the egg whites until soft peaks form. Gently fold the egg whites into the batter, taking care not to deflate them.
Cover the bowl with plastic wrap or a clean kitchen towel and let it rise in a warm place for about 1 hour, or until it has doubled in size.
Preheat your waffle maker according to the manufacturer's instructions.
Once the batter has risen, give it a gentle stir. Depending on your waffle maker's size, pour the appropriate amount of batter onto the hot surface and close the lid. Cook until the waffles are golden brown and crisp.
In a small saucepan over low heat, melt the cubed butter. Once melted, whisk in the whole milk, powdered sugar, and vanilla bean seeds (or paste/extract) until smooth.
Remove the waffles from the waffle maker and drizzle the warm glaze over the top while they are still warm.