Step‑by‑Step Instructions

• Preheat your oven to 350°F (175°C).
  
• In a medium bowl, mix together the chocolate cookie crumbs, melted unsalted butter, and granulated sugar until resembling damp sand.
  
• Press the mixture firmly into a 9-inch tart pan and bake for 10 minutes. Let it cool completely.
  
• Melt the dark chocolate in a microwave-safe bowl using 30-second intervals, stirring until smooth and set aside to cool.
  
• Whip 1 cup of heavy whipping cream until soft peaks form.
  
• Fold the whipped cream into the cooled melted dark chocolate gently until smooth.
  
• Beat the egg whites with a pinch of salt until medium peaks form, adding ¼ cup of granulated sugar until stiff peaks develop.
  
• Fold in the beaten egg whites into the chocolate mixture in two additions..
  
• Add the peppermint extract and gently fold until incorporated.
  
• Spoon the mousse into the cooled tart shell, smoothing the top with a spatula.
  
• Cover the tart and refrigerate for at least 4 hours, or until set.
  
• Whip the remaining 1 cup of heavy cream and spread over the tart. Garnish with crushed peppermint and chocolate shavings.