Preheat the oven to 350 degrees F. Prepare two cookie sheets with parchment paper. In a medium sized bowl, mix flour together with cocoa powder and salt until well combined.
In a separate medium sized bowl, cream together butter, brown sugar, one egg and vanilla extract.
Roll the dough into small 2 tsp sized balls and arrange on a prepared cookie sheet. Place about 12 cookies per sheet.
Make a small imprint in the centre of the cookies with your thumb, back of a teaspoon or with the rounded end of a wooden spoon. Bake for 7-8 minutes.
When you have the last tray of cookies in the oven, begin to melt white chocolate over low heat in a small saucepan with the heavy cream. Once melted, stir in peppermint extract.
Once the cookies have cooled slightly, add a small dollop of the white chocolate ganache to the centre indentation made in the thumbprint cookies and sprinkle with a few pieces of crushed candy cane. Allow the ganache to cool and set in the cookie. Enjoy!