• Beat the butter and powdered sugar until creamy and smooth. Add the peppermint extract, vanilla extract and egg. Beat well. 
• Add the flour and salt. Beat until well combined. 
• Divide the dough in half. 
• Stir the food coloring into half of the dough. Cover the dough and refrigerate for 2 to 4 hours. The chilled dough will be easier to work with.

To make the candy canes:

• Preheat the oven to 375°F. Line a baking sheet with parchment paper or spray with non-stick spray. 
• Measure one teaspoon of each color dough and roll into a 4-inch rope. Line a red rope up next to a white rope then twist them together. Pinch the ends slightly and place on the cookie baking sheet. Curve one end of the twisted rope to form a candy cane shape. Repeat with the remaining dough.
• For best results, place the baking sheet (with the cookies on it) in the fridge for 1 hour or in the freezer for 20 minutes. Chilling the cookies right before you bake them will keep them from spreading. You can skip this step if you are able to shape the candy canes quickly without warming the dough up with your hands.
• Bake for 8 to 10 minutes.
• Remove from the oven and sprinkle the crushed candy on the cookies while they are still warm. Let the cookies cool completely on the baking sheet. If the cookies cool down before the candy has a chance to stick to them, stick them back in the warm oven for 30 to 60 seconds. The crushed candy will start to melt and adhere to the cookies.