Step 1: Assemble the Sandwich

1. Layer the Fillings: Lay out 4 slices of bread. Place a slice of Swiss cheese on each, followed by a slice of ham and turkey. Top with another slice of Swiss cheese, then cover with the remaining bread slices to form 4 sandwiches.
2. Secure the Sandwiches: Gently press the sandwiches together. If needed, use toothpicks to hold them in place while cooking.

Step 2: Prepare the Batter

1. Whisk the Batter: In a shallow bowl or pie dish, whisk together the eggs, milk, salt, black pepper, nutmeg, and Dijon mustard (if using) until well combined.

Step 3: Dip and Cook the Sandwiches

1. Heat the Pan: Heat a large skillet or griddle over medium heat. Add butter and oil, swirling to coat the pan evenly. The combination of butter and oil helps prevent the butter from burning.
2. Dip the Sandwiches: Dip each sandwich into the egg batter, coating both sides evenly. Let any excess batter drip off.
3. Cook Until Golden: Place the dipped sandwiches in the skillet. Cook for 3-4 minutes per side, or until golden brown and the cheese is melted. Lower the heat if needed to prevent burning.

Step 4: Garnish and Serve

1. Dust with Powdered Sugar: Transfer the sandwiches to a cutting board. Slice each in half diagonally and dust with powdered sugar.
2. Serve with Jam: Serve the sandwiches warm with a side of raspberry or strawberry jam for dipping.