Spread softened butter evenly on the outside face of each bread slice. On the inside face of one slice, spread the Dijon mustard and on the other inside face spread the mayonnaise. This creates a thin, even layer that helps balance flavor and promotes even toasting.

Assemble filling

Place two slices of cheddar cheese onto the mayo-spread inside of one bread slice. Layer four slices of deli ham on top of the cheese, arranging them so they overlap and cover the bread. Sprinkle a pinch of black pepper over the ham. If using optional additions, add tomato slices, lettuce leaf, or pickle slices on top of the ham.

Close sandwich and toast

Top with the other bread slice, buttered side facing out. Heat a nonstick skillet or griddle over medium heat. Place the sandwich in the pan and cook 2–3 minutes until the bottom is golden brown and the cheese begins to melt. Press gently with a spatula or use a heavy pan lid to encourage even contact and melting. Flip and cook another 2–3 minutes until the second side is golden and the cheese is fully melted. If the bread browns before the cheese melts, reduce heat to low, cover the skillet with a lid for 1–2 minutes to trap heat and finish melting.

Serve

Remove sandwich from the pan and let rest 1 minute. Slice diagonally if desired and serve immediately.

Optional (oven method)

Preheat oven to 375°F (190°C). Assemble the sandwich as above but do not butter outside of bread. Place on a baking sheet, brush outside of bread lightly with melted butter or oil, and bake for 8–10 minutes, flipping once halfway, until bread is golden and cheese is melted.