Chocolate Ganache: Bring heavy cream to boiling in small heavy saucepan over medium-high heat. Remove from heat. Stir in chocolate pieces until melted and smooth. Stir in vanilla. Pour into 8- or 9-inch baking pan. Refrigerate until good spreading consistency, 2 hours.

Cake: Heat oven to 375 degrees F. Grease 9 x 3-inch springform pan; lightly flour bottom; line side of pan (not bottom) with waxed paper, cut to fit.

Sift together cake flour, baking powder and salt onto sheet of waxed paper.

Beat egg in small bowl until fluffy. Gradually add sugar, beating on high speed, until ribbons form, about 3 minutes. Gently stir in water and vanilla until well mixed.

Fold in flour mixture. Pour batter in prepared pan.

Bake in 375 degrees F oven for about 7 minutes or until cake is golden and center springs back when lightly pressed with fingertip. Cool cake in pan on wire rack.

Layers: Remove 1 pint vanilla ice cream to refrigerator to soften for about 30 minutes.

Beat nuts and pudding into softened ice cream in large bowl. Spread over cake. Freeze 3 hours, until firm.

Spread 1-1/8 cups Chocolate Ganache over top of hardened pistachio ice cream in pan. Freeze until firm, about 4 hours.

Remove 1 pint vanilla ice cream to refrigerator to soften for about 30 minutes.