Preheat the waffle iron. Set it to medium or medium-high. A properly heated iron is the key to crisp edges.

Whisk the dry ingredients. In a large bowl, combine the flour, protein powder, cornstarch, flaxseed, baking powder, baking soda, and salt. Break up any clumps so it’s evenly mixed.

Mix the wet ingredients. In a separate bowl, whisk the egg, milk, Greek yogurt, maple syrup, and vanilla until smooth.

Combine wet and dry. Pour the wet mixture into the dry. Stir gently until just combined. If the batter looks too thick, add 1–2 tablespoons more milk. You want a pourable, slightly thick batter.

Fold in the blueberries. Add them gently to avoid streaking the batter. If using frozen, toss them with a teaspoon of flour first to help prevent color bleed.

Grease and pour. Lightly oil the waffle iron or use nonstick spray. Add enough batter to cover the grates without overflowing. Close the lid.

Cook until deeply golden. Most irons take 3–5 minutes. Don’t peek early—steam escaping and a browned exterior are signs they’re ready. They should release easily when done.

Rest on a rack. Place finished waffles on a wire rack so they stay crisp while you cook the rest. Avoid stacking right away.

Serve warm. Top with a pat of butter, a drizzle of maple syrup, extra blueberries, or a dollop of Greek yogurt for extra protein.