1. Prepare the Apples: Wash, core, and thinly slice your apple. Aim for slices about 1/8-inch thick so they cook quickly and evenly. A mandoline slicer can help achieve uniform slices, but a sharp knife works just as well.

2. Butter the Bread: Lightly spread softened butter on one side of each sourdough bread slice. This buttered side will be placed face down on your cooking surface.

3. Assemble the Toast: On the unbuttered side of two sourdough slices, layer half of the shredded or sliced cheddar cheese. Arrange half of the apple slices evenly over the cheese. If using, sprinkle half of the cinnamon and brown sugar over the apples.

4. Top with More Cheese: Place the remaining cheddar cheese over the apple slices on both assembled toasts. This helps to hold the apples in place and creates a delicious cheesy crust.

5. Cook the Toast: Heat a large skillet or griddle over medium heat. Carefully place the two assembled toasts, buttered-side down, into the hot pan. Cook for 5-7 minutes, or until the bottom is golden brown and the cheese is starting to melt.

6. Finish Cooking: Gently flip the toasts. Continue to cook for another 5-7 minutes, or until the second side is golden brown, the cheese is fully melted and bubbly, and the apples have softened slightly.

7. Serve Immediately: Remove the toasts from the skillet and let them cool for a minute or two before slicing and serving. The cheese will be hot, so be careful!