Follow the steps in order for the best result.
To prepare the raspberry jelly sauce, combine the raspberry jelly, water, and half-and-half in a blender. Blend until the mixture is smooth and well combined. This should yield approximately 3/4 cup of sauce.
For the batter, in a mixing bowl, add water, egg, salt, white pepper, and yellow food coloring. Using an electric mixer set on low speed, thoroughly combine the ingredients. Incorporate the all-purpose flour and baking powder into the mixture, continuing to mix until a smooth batter forms. Once prepared, chill the batter. This quantity will be sufficient for coating four sandwiches.
To assemble the sandwiches, create four individual sandwiches by layering the swiss cheese between the ham and turkey slices. Cut each sandwich into fourths, and secure each quarter with a toothpick.
In a deep fryer or large pot, heat approximately 6 inches of vegetable oil to a temperature of 340°F (170°C). Dip each sandwich quarter into the chilled batter, ensuring all surfaces are evenly coated. Carefully place the battered sandwiches into the hot oil and deep fry until they achieve a golden-brown color, turning as necessary to ensure even cooking. Once golden brown, remove the sandwiches from the oil and allow any excess oil to drain off. Remove the toothpicks, sprinkle the sandwiches generously with confectioners' sugar. Serve immediately with the prepared raspberry jelly sauce for dipping.