Servings: Serves 12

½ cup (125 mL) Irish whiskey ½ cup (125 mL) Irish whiskey
6 oz (175 g) bittersweet (70% cocoa) chocolate, chopped 6 oz (175 g) bittersweet (70% cocoa) chocolate, chopped
1 tbsp (25 mL) instant espresso powder dissolved in 1/3 cup (75 mL) hot water 1 tbsp (25 mL) instant espresso powder dissolved in ⅓ cup (75 mL) hot water
1/3 cup (75 mL) toasted, ground walnuts ⅓ cup (75 mL) toasted, ground walnuts
1/3 cup (75 mL) all-purpose flour ⅓ cup (75 mL) all-purpose flour
½ tsp (2 mL) salt ½ tsp (2 mL) salt
½ cup (125 mL) unsalted butter, softened ½ cup (125 mL) unsalted butter, softened
1 tbsp (15 mL) vanilla 1 tbsp (15 mL) vanilla
½ cup (125 mL) granulated sugar ½ cup (125 mL) granulated sugar
3 eggs, separated 3 eggs, separated
 
Icing Icing
2 oz (60 g) dark chocolate, chopped 2 oz (60 g) dark chocolate, chopped
2 tbsp (25 mL) Irish whiskey 2 tbsp (25 mL) Irish whiskey
¼ cup (50 mL) cold butter, cubed ¼ cup (50 mL) cold butter, cubed

1. Preheat oven to 350°F (180°C). Butter and flour an 8-inch (2-L) springform pan. Set aside.
2. In a saucepan, bring ½ cup (125 mL) whiskey to boil over medium-high heat until it reduces in half, about 5 minutes. Transfer to metal bowl and add chopped chocolate and espresso mixture. Place bowl over a saucepan of simmering water and stir until mixture is smooth, about 2 minutes. Remove bowl from on top of water and set aside.
3. In a bowl, whisk together walnuts, flour and salt. Set aside.
4. Using an electric mixer, beat butter, vanilla and sugar until light and fluffy. Beat in egg yolks, 1 at a time, beating well after each addition. Fold in chocolate mixture. Using clean, dry beaters, beat egg white in bowl until stiff peaks form. Fold one-third of the whites into the batter with one-third of the flour mixture in 3 additions. Transfer batter to prepared pan, gently smoothing top with spatula.
5. Bake in the centre of the oven until a tester inserted in the centre comes out clean, about 40 minutes. Cool in pan on rack for 30 minutes and then remove pan collar to cool completely.
6. For icing, in a small bowl, combine chocolate and whiskey. Place over a saucepan of simmering water and stir until smooth. Add butter piece by piece, waiting until each piece is melted before adding the next. Let thicken slightly and drizzle over cake.