Line a baking sheet with paper towels and top with a wire cooling rack.
Add 1-2 inches of vegetable or canola oil to a large heavy bottomed pot over MED heat until about 350 degrees F.
While oil is heating up, make sandwiches.
Start with one slice of bread, slather with mustard, top with turkey, top with slices of cheese, top with ham, and finish with another slice bread slathered with mustard (mustard side down).
To keep the sandwich from falling apart, use toothpicks to secure the corners of the sandwich.
To a large mixing bowl, add the egg and beat with a whisk. Add in flour, baking powder, sugar, salt and water. Whisk until smooth.
Dip secured sandwich in batter, making sure to coat all sides.
Carefully lower sandwich into the hot oil and fry for several minutes per side, or until golden brown.
Remove sandwich from oil and place on top of the prepared cooling rack.
Immediately before serving, dust with powdered sugar.
Serve with raspberry preserves for dipping.