1. Butter one side of each slice of sourdough bread, spreading the butter all the way to the edges.

2. In a small bowl, stir together the Dijon mustard and honey until smooth to make a sweet-tangy spread.

3. Flip the bread so the unbuttered sides face up. Spread the honey-Dijon mixture over the unbuttered sides of all four slices.

4. Layer sliced smoked Gouda over two of the bread slices, covering the surface evenly.

5. Arrange the thin apple slices over the cheese in a shingled layer so every bite gets some apple. Sprinkle lightly with kosher salt, black pepper, and a pinch of ground cinnamon if using.

6. Top each loaded slice with the remaining bread slices, keeping the buttered sides facing outward.

7. Heat a nonstick or cast-iron skillet over medium heat. When hot, add the sandwiches, buttered side down.

8. Cook for 3 to 4 minutes per side, adjusting the heat as needed, until the bread is deeply golden and crisp and the cheese is fully melted.

9. Transfer sandwiches to a cutting board and let rest for 1 minute so the cheese can settle slightly.

10. Slice each sandwich in half or into quarters and serve immediately, with an extra drizzle of honey if desired.