In a mixing bowl, combine softened salted butter, Dijon mustard, yellow mustard, and finely chopped cornichons. Mix thoroughly until well incorporated.

Using a butter knife, spread the mustard mixture on one side of each slice of bread evenly.

Place a slice of Muenster cheese on top of the mustard-coated side of one of the bread slices.

Layer a slice of corned beef on top of the Muenster cheese.

Take a second slice of bread and place it on top of the corned beef, mustard-side down.

Trim the crusts and cut each sandwich in half diagonally or into thirds.

Arrange the sandwiches on a serving tray and pair with black tea.