01 -
Melt butter, whisk in cornstarch, salt, and pepper until bubbly. Gradually add milk in thirds, allowing sauce to thicken between additions.
02 -
Butter outside of bread slices. Spread inside with Dijon, layer with ham and cheese. Close sandwiches.
03 -
Cook sandwiches on griddle or non-stick pan until golden and cheese melts.
04 -
Top sandwiches with white sauce and shredded cheese. Broil until brown and bubbly.