With a food processor or in a large zip-topped bag with a rolling pin, crush the chocolate sandwich cookies to crumbs.
Place the chocolate and ¼ cup heavy cream in a bowl. Set over pot of simmering water and melt until smooth, stirring often. (This can also be done in a double boilder.) Set aside to cool to room temperature.
Beat remaining heavy cream to soft peaks. Gently fold the whipped cream into the chocolate in 2-3 additions, gently folding each addition in until no streaks of chocolate remain.
Layer the Oreo crumbs and chocolate into 4 glasses. Top with more whipped cream and a cookie, if desired.
Serve immediately or store in the fridge for up to 24 hours.
Calories: 468kcal, Carbohydrates: 17g, Protein: 4g, Fat: 43g, Saturated Fat: 27g, Polyunsaturated Fat: 2g, Monounsaturated Fat: 11g, Trans Fat: 0.02g, Cholesterol: 103mg, Sodium: 27mg, Potassium: 246mg, Fiber: 2g, Sugar: 13g, Vitamin A: 1326IU, Vitamin C: 1mg, Calcium: 76mg, Iron: 2mg