Special equipment: a mandoline, a piping bag with a star tip
In a stand mixer (or with an electric hand mixer), beat together the cream cheese, ranch seasoning and 1 cup of the mayonnaise until easily spreadable. Put one-third of the mixture into a piping bag with a star tip.
With a serrated knife, trim the sides of the boule until it is an even cylinder. Cut the cylinder across the radius into four 1-inch slices. Choose a serving platter and place a slice of bread in the center for the bottom layer. Position 4 squares of parchment underneath the bread to keep the serving platter clean once you begin icing.
Spread 1 tablespoon of the mustard onto the top of the bread. Top with the Cheddar, then the ham and turkey. Add half of the lettuce on top of the turkey. Spread the remaining 1 tablespoon mustard on one side of another slice of bread, then place it mustard-side down on top of the lettuce.
Spread the top of the bread with 2 tablespoons mayonnaise. Top with the bacon, tomato and remaining shredded lettuce. Spread the remaining 2 tablespoons mayonnaise on a third slice of bread, then place it mayonnaise-side down on top of the lettuce. Next, cover the top of the bread with the potato chips in a single layer. Top the potato chips with the chicken salad and then the last slice of bread.
With a knife or offset spatula, spread the cream cheese mixture along the top and sides of the cake evenly. Pipe rows of stars onto the top and bottom edge of the cake.
Decorate the cake using radish and cucumber slices in a ring around the top and bottom of the cake. Shape the remaining radish and cucumber slices into roses and press into the top of the cake.
Serve chilled or at room temperature. Can be made ahead and refrigerated for 1 to 2 hours.