Make the Herbed Butter: Mix softened butter, minced garlic, onion, sesame seeds, poppy seeds, and sea salt in a small bowl until combined.
Prep Ingredients: Lay out bread slices, corned beef, cheese, Russian dressing, and sauerkraut. Drain sauerkraut to avoid soggy bread.
Butter the Bread: Spread herbed butter on one side of each slice of bread. This will be the toasted side.
Assemble the Sandwich: Spread Russian dressing on the unbuttered side of the bread. Add 2 slices of Swiss cheese, corned beef, sauerkraut, and another slice of cheese. Top with another slice of bread, buttered side out.
Grill the Sandwich: Heat a skillet over medium heat. Grill the sandwich for 3-4 minutes on each side until the bread is golden and the cheese is melted.
Serve: Let the sandwich rest for a minute, slice in half, and enjoy with your favorite sides.