Method

Grease 8-inch (2 L) springform pan; line bottom with parchment or waxed paper. Set aside.

In large bowl, beat butter with sugar until light and fluffy. Beat in egg and vanilla. In second bowl, whisk together flour, cocoa powder, baking powder, baking soda and salt. With wooden spoon, stir into butter mixture alternately with buttermilk, making 3 additions of dry ingredients and 2 of liquid.

Spoon into prepared pan, smoothing top. Bake in centre of 350°F (180°C) oven for 35 to 40 minutes or until cake tester inserted in centre comes out clean. Let cool in pan on rack for 20 minutes. Remove from pan; let cool completely on rack. Carefully peel off paper.

Filling: In heatproof bowl, beat egg yolks with sugar for 5 minutes. Whisk in liqueur. Place over saucepan of simmering water; cook, whisking, for about 3 minutes or until thickened. Let cool. Beat in cheese until smooth. Whip cream; fold one quarter into cheese mixture, then fold in remaining cream.

Cut 27- x 4-inch (68 x 10 cm) strip of waxed paper; fit around clean springform pan to line side and extend above top. Cut cake in half horizontally. Place bottom half in pan, cut side up.

Topping: In small bowl, stir together coffee liqueur, 1 tablespoon (15 mL) water and instant coffee granules until dissolved. Brush half over cake in pan. Pour half of the filling over top. Place top half of cake over filling, cut side down. Brush remaining topping over cake; pour remaining filling over topping. Sprinkle with cocoa. Freeze for at least 8 hours or until solid. Freeze for at least 8 hours or until solid. (Make-ahead: Freeze in airtight container for up to 2 weeks.)

Thaw in refrigerator for 2 hours. Remove pan side and paper; transfer to flat serving plate. With vegetable peeler, peel curls from chocolate; arrange decoratively over top.