In a bowl, combine buttermilk and oats. Let the mixture sit for 15 minutes to soften the oats. Add the egg, vegetable oil, and vanilla extract and whisk together until well combined.

In another bowl, mix together the flours, starches, and nuts to create the dry ingredients base.

Gently fold the dry ingredients into the wet mixture until just combined. Be careful not to overmix; a few lumps are okay. Let the batter rest in the refrigerator for about 10 minutes.

While the batter is resting, preheat your waffle iron. Once heated, lightly brush the waffle grids with vegetable oil to prevent sticking.

Spoon an appropriate amount of batter onto the preheated waffle iron according to your iron's size and instructions. Close the lid and cook until the light indicates they're ready or until golden brown and crisp.

Serve immediately with fresh fruit, maple syrup, and/or whipped cream. Or, see freezing instructions.