Peppery pastrami piled high on seeded rye with deli mustard is a high protein New York deli essential. This iconic sandwich delivers smoky, savory satisfaction in every bite.
Spread half the butter evenly on one side of each slice of rye bread.
Place a nonstick skillet or griddle over medium heat. Once hot, lay the bread slices buttered side down.
Layer 4 oz of pastrami on each of two bread slices, piling high to create volume and ensure an even heat through.
Top pastrami with a slice of Swiss cheese (if using), then spread 1 tbsp mustard onto the remaining bread slices.
Close the sandwiches, press gently, and cook 2–3 minutes per side, pressing occasionally until the bread is crisp and the cheese has melted. Slice in half and serve immediately.