Heat a panini press or cast iron pan over medium-high heat.
Divide cheddar evenly between two slices of whole grain bread, followed by 2 slices of apple and 2 slices of smoked turkey. Spread remaining two slices of bread with honey mustard and place on top of the turkey (mustard side down).
Place sandwiches in heated panini press or cast iron pan and grill for 4 to 5 minutes turning as necessary to evenly brown the bread on both sides of the sandwich.
Once cheese is melted and bread is golden brown, remove sandwiches from the heat.
Remove tops of sandwiches, add spinach, replace tops and serve immediately.
Per serving: 410 calories, 27 g protein, 15 g fat (9 g saturated fat), 43 g carbohydrates, 7 g fibre, 60 mg cholesterol, 1020 mg sodium, %RDI:Iron 10%, Calcium 35%, Vitamin A 15%, Vitamin C 10%