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1
For cake:
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2
Position rack in center of oven and preheat to 350u00b0F.
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3
Butter and flour two 9-inch-diameter cake pans with 1 1/2-inch-high sides.
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4
Blend 1/2 cup walnuts, 1 tablespoon sugar, and espresso in processor until nuts are finely ground.
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5
Whisk flour, cocoa, baking powder, cinnamon, baking soda, and salt in medium bowl to blend. Using electric mixer, beat butter in large bowl until smooth.
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6
Gradually add remaining sugar (1 1/4 cups minus 1 tablespoon), beating until fluffy. Beat in eggs, 1 at a time, then egg yolk. Add ground walnut mixture and vanilla; beat to blend.
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7
Reduce mixer speed to low and beat in dry ingredients in 3 additions alternately with buttermilk in 2 additions.
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8
Fold in remaining 1/2 cup walnuts.
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9
Divide batter evenly between prepared pans.
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10
Bake cake layers until tester inserted into center comes out clean, about 26 minutes. Cool in pans 5 minutes, then turn out onto racks and cool completely.
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11
For coffee-mascarpone cream:
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12
Stir espresso, cinnamon and 1 tablespoon water in large bowl until coffee dissolves.
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13
Add cream, mascarpone, sugar, and vanilla. Beat until filling is thick and smooth (do not overbeat or filling may curdle).
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14
Place 1 cake layer on platter, flat side up. Spread half of filling over cake.
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15
Place second layer, flat side down, on filling.
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16
Spread remaining filling over top. Mix walnuts, cinnamon, and salt.
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17
Sprinkle over top of cake.
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18
Cover with cake dome.
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19
Chill at least 1 hour and up to 1 day.
