1. Butter a 3- to 4-quart ceramic or porcelain bowl. Set aside. In the work bowl of a food processor fitted with the grating disc, grate the walnuts. Set aside.

2. Beat the egg yolks in an electric mixer or with a whisk until very light. Add the sugar and beat for 1 minute longer at medium-high speed.

3. Again, fit the work bowl with the grating disc and grate the chocolate. Leaving the grated chocolate in the work bowl, remove the disc and set the steel blade firmly in place. Add the flour, cinnamon and cloves and process until very well mixed to almost a chocolate flour, about 30 seconds.

4. Pour flour mixture into the beaten egg yolk mixture and stir hard until well combined. Add the walnuts and mix well.

5. Bring a kettle of water to a boil. In a separate bowl, beat the egg whites until they hold a stiff peak. Stir about a quarter of the beaten whites into the chocolate mixture to lighten it, then gently fold the remaining whites into the batter. Fold just until mixed.

6. Pour the batter into the prepared bowl and cover tightly with foil. Pour 2 inches of boiling water into a large pot. Place prepared bowl inside pot. Cover pot and steam for 2 hours. Unmold while hot.

7. Serve hot accompanied by cream or whipped cream, if you wish. Alternately, serve cold with a cold Crème Anglaise.