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1
Preheat oven to 350.
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2
Butter mold and dust with sugar, knocking out excess.
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3
Stir together ground almonds, chocolate, and spices in a bowl.
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4
Beat yolks with 1/4 cup sugar in another bowl with an electric mixer until thick and pale, then beat in zest.
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5
Beat whites with salt with cleaned beaters in a large bowl until they just hold soft peaks.
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6
Gradually beat in remaining 1/4 cup sugar and beat until whites just hold stiff peaks.
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7
Stir one third of whites into yolk mixture to lighten, then fold in remaining whites in 2 more batches.
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8
Fold in ground almond mixture.
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9
Pour batter into mold and bake in middle of oven until golden and a tester comes out clean, about 45 minutes.
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10
Cool cake in mold on a rack 10 minutes, then invert onto rack and cool completely.
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11
Melt chocolate with 1 tablespoon butter in a small heavy saucepan over very low heat, stirring.
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12
Remove from heat and add remaining 5 tablespoons butter, 1 tablespoon at a time, stirring until smooth.
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13
Transfer icing to a bowl and chill, covered, until slightly thickened and spreadable, about 30 minutes.
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14
Spread icing over cake with a small metal spatula.
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15
Stick points of almonds into cake in straight rows, following ridges, to resemble a porcupine.
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16
Chill cake until icing is set, at least 1 hour.
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17
Transfer cake to a platter and bring to room temperature before serving.
