Preheat your Belgian waffle maker according to manufacturer instructions. If your maker has temperature settings, set to medium-high heat.

In a large bowl, whisk together flour, vanilla protein powder, baking powder, cinnamon, and sea salt.

In a medium bowl, whisk egg yolks, milk, Greek yogurt, melted butter, maple syrup, and vanilla extract until smooth.

In a separate clean glass bowl, beat egg whites with an electric hand mixer for 2 minutes until stiff, glossy peaks form.

Pour wet ingredients into dry ingredients and gently stir with a spatula just until combined (do not overmix). Gently fold in the whipped egg whites in two batches until batter is airy.

Lightly brush or spray the waffle iron grids with avocado oil. Pour about 1/2 cup batter onto the center of the iron, close lid, and cook for 4 to 5 minutes until steam stops and the waffle is golden brown and crisp.

Transfer waffle to a wire rack in a 200°F (95°C) oven to keep exceptionally crisp while cooking remaining batter. Serve immediately with warm maple syrup, fresh berries, and a pat of butter!