Place the brown rice flour, oat flour, tapioca starch, potato starch, psyllium husk powder, baking powder, and kosher salt in a medium bowl. Whisk until combined.

Whisk the granulated sugar, melted butter, eggs, whole milk, and sourdough starter discard in a large bowl until combined.

Next, add the gluten-free flour mixture to the wet ingredients and whisk until combined.

Set a large cast-iron skillet over a medium-low flame.

Place 1 teaspoon of butter in the skillet and let it melt. Use a mini soup ladle or 1/4 cup measuring cup into the skillet.

Let the pancake cook for 2-3 minutes until bubbles form on the surface of the pancake.

Flip the pancake over and cook it for another 2-3 minutes until the other side is browned. Place the pancake on a large plate and set it aside.

Repeat steps 5-7 until all the pancake batter is gone.

Serve the pancakes with butter and pancake syrup if desired.