Servings: One 9-inch (23 cm) square pan, which cuts into 25 to 36 bars
4 oz (120 g) bittersweet chocolate, chopped
2 large egg whites, at room temperature
¼ tsp (1 mL) salt
½ cup (125 mL) water
2 cups (420 g) sugar
½ cup (125 g) white or golden corn syrup
1 tsp (5 mL) vanilla extract
4 oz (120 g) milk chocolate, chopped
3 Tbsp (45 g) unsalted butter
1 Tbsp (15 g) white corn syrup
1. Preheat the oven to 350°F (180°C). Grease and line a 9-inch (23 cm) square pan with parchment paper so that the paper comes up the sides.
2. Prepare the crust by stirring the cookie crumbs, icing sugar, cocoa powder and flour together. Add the melted butter and stir until fully combined. Press this into the bottom of the prepared pan and bake the crust for 10 minutes. Cool the crust while making the filling.
3. Melt the chocolate in a bowl resting over a pot of barely simmering water, stirring until melted. Set aside to cool. Whip the whites and salt in a large bowl until they just begin to hold a soft peak and set aside.
4. Pour the water into a medium saucepot, and then add the sugar and corn syrup. Without stirring, bring the mixture to a boil and continue to boil over high heat while brushing the sides of the pot with water until the sugar reaches a temperature of 255°F (124°C). Remove the sugar from the heat and carefully pour it into the whipped egg whites while beating on medium-high speed until fully added. Continue whipping the mixture until it cools almost to room temperature, about 7 minutes. Beat in the chocolate and vanilla and quickly spread this over the cooled crust (you can use a lightly greased spatula to spread the candy evenly) and chill for an hour.
5. To prepare the topping, melt the milk chocolate, butter and corn syrup in a bowl placed over a pot of barely simmering water, stirring until melted. Pour and spread the chocolate over the filling and chill to set.
Portion the bars while chilled, but they can be stored in an airtight container at room temperature for up to 3 days.