Prep the ingredients per the instructions above.
(Optional) Toast the slices of sourdough bread to your desired level of crispness.
Spread mayonnaise and mustard on one side of each slice of bread.
Layer the bread with romaine lettuce, tomato slices, deli ham, and Swiss cheese.
Top each sandwich with the remaining slices of bread, mayonnaise side down. Press gently, then cut each sandwich in half.
In a blender, add banana, maple syrup, vanilla extract, and cold milk. Blend until smooth and creamy.
Serve the sandwich with chips, pickles, and Korean banana milk.