Preheat oven to 375 degrees and grease a bread pan with nonstick cooking spray.
In a medium bowl, combine the cocoa powder and chocolate chips. Add boiling water. Stir until well combined and the chocolate chips are melted. Set aside and allow to cool.
In a medium bowl, whisk together the flour and salt. Set aside.
In a large bowl, beat together the butter and sugar until light and fluffy. Add the eggs, one at a time, beating between each addition.
Mix in the chocolate mixture and peppermint extract until well combined.
Add the flour mixture and beat to combine.
Pour the batter into the prepared bread pan and bake in the preheated oven for 60 to 70 minutes, until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for five to 10 minutes, then remove from pan and allow to cool on a wire rack until completely cool.
When the cake is cool, prepare the topping by melting the butter and cocoa powder in a small saucepan, stirring constantly. When the butter is melted and the chocolate is well combined, remove from heat and add the powdered sugar, peppermint extract, and one tablespoon of hot water. Stir to combine. Add more water as needed until desired consistency is reached.
Spread the mixture over the top of the cooled cake, then top with crushed peppermint candy.
Enjoy this delicious dessert anytime you want a sweet treat!