For the Sage Butter:

1. Melt the butter in a medium saucepan over medium heat. Add the sage once the butter is melted and lower the heat. Swirling the pan, cook until the butter is starting to brown and the sage leaves crisp up.
2. Remove from the heat and season with salt. Spoon out the crispy sage leaves and set on a plate lined with paper towels.
3. Allow to cool slightly before using with the sandwiches.

For the Sandwiches

1. Heat a large skillet over medium-low heat.
2. Assemble each sandwich by dividing the two cheeses evenly between four of the slices of bread.
3. If desired, spread a little mustard on the remaining four slices of bread.
4. Add a few crispy sage leaves to each sandwich and then top with the mustard-coated slices of bread, pressing down lightly to form the sandwiches.
5. Brush the outside of the bread slices with the sage butter and add them to the pan. I like to add a drizzle of the butter directly to the pan as well, to really drive home that sage flavor.
6. Cook until the bread is crisp and golden and the cheese is starting to melt. Flip and do the same on the other side.
7. Serve immediately while the cheese is warm and gooey.