If you prefer the sandwich lightly toasted, spread the softened butter evenly on the outside faces of both sourdough slices. Heat a skillet over medium heat until hot but not smoking.

Toast bread (optional)

Place bread slices butter-side-down in the hot skillet. Toast 1–2 minutes until golden brown, then flip and toast the other side 1 minute. Remove and set aside. If you do not want toasted bread, skip the butter and toasting.

Assemble spreads

On the non-toasted (or untoasted) interior face of one bread slice, spread the mayonnaise evenly. On the other interior face, spread the Dijon mustard evenly.

Layer fillings

Place the leaf lettuce on the mayonnaise-lined slice first to create a moisture barrier. Top with the turkey slices, arranging them to cover the bread evenly (about 4 oz). Lay the two Swiss cheese slices over the turkey. Add the tomato slices and red onion rings on top of the cheese. Season the tomato slices with a light pinch of salt and grind of black pepper (use the measured quantities across the sandwich).

Finish sandwich

Place the mustard-spread bread slice on top of the layered side to close the sandwich. Press gently to compact the layers slightly.

Optional warm melt

If you want the Swiss slightly melted, return the assembled sandwich to the skillet over low heat, cover loosely with a lid, and warm for 1–2 minutes until the cheese softens. Flip and warm the other side 30–60 seconds if needed. Remove from heat.

Slice and serve

Using a sharp knife, cut the sandwich in half diagonally or down the middle. Serve immediately with optional dill pickle spear and potato chips.

Spread & Seasoning

Measure and combine the mayonnaise (1 tbs) and Dijon mustard (1 tsp) separately so each can be spread on one slice of bread. Use the salt and black pepper to season the tomato after it is layered; do not over-salt the meat.

Optional (for serving)

Arrange the dill pickle spear and potato chips on the plate alongside the sandwich for a classic deli-style accompaniment.