Preheat your waffle iron according to manufacturer directions. In a large bowl, whisk together flour, sugar, baking powder, and salt.

Separate the eggs. Add the yolks to a separate bowl with the warm milk, oil (or melted butter), and vanilla. Whisk until smooth.

Pour the wet mixture into the dry ingredients and stir until just combined. A few lumps are perfectly fine.

In a clean bowl, beat the egg whites with an electric mixer until stiff peaks form. This is the step that makes these waffles truly special — extra light and crispy.

Gently fold the beaten egg whites into the batter using a rubber spatula. Do not overmix — you want to keep as much air as possible.

Pour batter into the preheated waffle iron and cook according to your machine (usually 3-5 minutes) until golden brown and steam stops rising. Serve immediately.