01 - Combine softened butter and ground cinnamon in a small mixing bowl until evenly blended.
02 - Spread the cinnamon butter evenly over one side of each bread slice.
03 - If desired, spread a thin layer of cream cheese and/or honey on the unbuttered side of two bread slices.
04 - Place one slice of cheddar cheese onto the unbuttered side of each prepared bread slice. Arrange apple slices evenly over the cheese, and sprinkle with a pinch of sea salt if desired.
05 - Top apples with remaining cheddar cheese slices. Close the sandwiches with the other bread slices, ensuring the buttered sides are facing outward.
06 - Preheat a nonstick skillet or griddle over medium heat.
07 - Place sandwiches in the skillet and cook for 3 to 4 minutes per side, gently pressing with a spatula, until the bread is golden brown and the cheese has melted completely.
08 - Remove sandwiches from the skillet, slice in half, and serve immediately.