Sugar-Reduced Chocolate Walnut Buche de Noel

In small bowl, whisk together walnuts, flour, baking powder, salt and cinnamon; set aside.

Separate 3 of the eggs, dropping yolks and whites into separate large bowls. Beat egg whites until foamy; beat in 1/4 cup (50 mL) of the sugar, about 1 tbsp (15 mL) at a time, until soft peaks form.

Beat together egg yolks, remaining eggs and remaining sugar until pale and thick enough that batter leaves ribbons on surface when beaters are lifted, about 5 minutes. Fold in one-third of the whites; fold in remaining whites. Fold in walnut mixture just until combined. Add butter and orange rind; fold in just until combined. Spread on parchment paper–lined 15- x 10-inch (40 x 25 cm) rimmed baking sheet.

Bake in centre of 350°F (180°C) oven for about 12 minutes or until golden and cake springs back when lightly touched. Loosen edges with knife; invert onto icing sugar-dusted tea towel, aligning 1 short edge of cake with edge of towel. Starting at corner, carefully peel off paper. Starting at short side, roll cake up loosely in towel; let cool on rack. (Make-ahead: Wrap in plastic wrap; store for up to 24 hours.)

Icing: In small saucepan, bring cream to boil. Pour over chopped chocolate in bowl, whisking until smooth. Stir in vanilla. Refrigerate until cold, about 4 hours. (Make-ahead: Refrigerate for up to 24 hours.) Stir in sugar; beat just until texture of soft icing.

Unroll cake; spread with 1-1/2 cups (375 mL) of the icing. Reroll without towel; place, seam side down, on flat serving platter. Starting 1 inch (2.5 cm) from 1 end of cake, cut off end on sharp diagonal. Press cut side onto long side close to uncut end of cake.

Spread remaining icing all over log. Refrigerate until cold, about 2 hours. (Make-ahead: Cover loosely and refrigerate for up to 6 hours.)