In a heavy saucepan, heat semisweet and milk chocolates, whipping cream and coffee crystals over low heat unitl melted, stirring constantly. Cool to room temperature.
In a large mixing bowl beat eggs, coffee liqueur and vanilla with a electric mixer on low speed till combined. Add flour and sugar. Beat on medium to high speed for 8 minutes. (the batter should be light and slightly thickened.) Fold about quarter of the mixture into chocolate mixture. Fold chocolate mixture into remaining egg mixture. Fold in nuts.
Grease and flour the bottom and sides of a 23 cm springform pan. Spread batter into pan. Bake in a 325 oven for 40 to 45 minutes or until slightly puffed around the outer edge (center will be slightly soft). Cool in pan on a rack for 20 minutes. Remove sides of pan. Cool. Cover and chill for up to 24 hours.
To serve, let stand at room temperature for 30 minutes. Top with Mocha Cream and if desired, coffee beans.
Mocha Cream: In a chilled small mixing bowl combine both ingredients and with chilled beaters, beat on medium to high speed just until stiff peaks form.