Step 1
In a small bowl, combine all pepper mayonnaise ingredients.
Step 2
Spread butter over one side of each slice. Lay the buttered sides down on a cutting board or work area.
Step 3
Layer the cheese on 4 slices of bread, then top with turkey, tomato, and spinach.
Step 4
Spread remaining bread with pepper mayonnaise, then top all the sandwiches, buttered side up.
Step 5
Grill the sandwiches using a panini press or medium skillet while pressing down on the top of the sandwich with another pan.
Step 6
Cook until golden brown on both sides and cheese is melted.
Step 7
Repeat with remaining sandwiches.
Step 8
Cut in half and serve warm.
