Begin by slicing your potato flake sourdough into 1 inch thick slices.
Next, in your small square or rectangle dish, whisk your eggs. Add milk, sugar, vanilla, and salt. Whisk until combined.
Heat your cast iron skillet or griddle over medium heat. Grease with about 1 tablespoon of butter. You will likely need to add more butter after each batch of french toast.
Dip each slice of bread in the egg mixture for about 30 seconds each side, for a total of 1 minute.
Lift the bread up and let a bit of the excess drip off and transfer to the skillet. cook for 4-5 minutes on each side, or until golden brown.
Continue to do this until you have run out of the egg mixture. You can usually get about 8-10 slices.
Serve with a pat of butter on the top of your stack and drizzled with some maple syrup. Enjoy!