In a small bowl, combine Dijon mustard and honey, stirring until smooth. Adjust the sweetness with more honey if desired.

Take two slices of whole grain bread and spread honey-Dijon mixture on one side of each slice. Layer turkey, cheddar, apple, and optional greens on one slice, seasoning with salt and pepper before topping with the second slice, spread side down.

Spread butter evenly on the outer sides of the sandwich to achieve a golden crust when grilling.

Preheat the panini press or skillet over medium heat and grill the panini for about 3-5 minutes until the bread is golden brown and cheese is melted.

Once grilled, carefully remove the panini and allow it to rest for a minute before slicing it diagonally.