To make the raspberry sauce, combine the raspberries, water, and sugar in a small saucepan over medium-low heat. Simmer until the raspberries have softened and broken down and the sauce has thickened. Remove from the heat and set aside to cool.

In a shallow dish, whisk together the milk and egg until smooth. Dip one side of each slice of bread into the milk and egg mixture. On the dry side, spread mayonnaise and mustard to taste.

Heat a frying pan over medium heat. Place one slice of bread in the pan, soaked side down. Top with Swiss cheese, deli ham, and deli turkey. Add the second slice of bread, with the soaked side facing up. Cook until the bottom is golden brown, then flip and cook until the second side is golden and the cheese is melted.

Slice the sandwich in half and serve warm with the raspberry sauce for dipping.