In a large microwave-safe bowl combine marshmallows and milk, then place into the microwave. Heat in 30 second increments for 1 ½ minutes, stopping to stir every 30 seconds. Remove from the microwave and let cool down slightly.
Once slightly cooled, but still warm, mix in the vanilla, peppermint extract, and salt.
Add the food coloring in drops, mixing after each drop, until the desired color is reached.
Fold in 1 cup of cool whip and most of the crushed candy canes.
Remove the crust from the refrigerator, then transfer the filling mixture into the cooled crust. Top with the remaining cool whip, swirling it into the mixture with a knife or toothpick to make a design.
Top with additional candy cane pieces, then cover with plastic wrap and place into the refrigerator to chill for at least 4 hours before serving.