For custard, in a medium saucepan combine egg yolks, milk, and the 2/3 cup sugar. Cook and stir over medium heat just until mixture coats the back of a clean metal spoon. Place saucepan in a large bowl of ice water and stir frequently until mixture is cool. Stir in lemoncello and lemon peel; set aside.
In a large bowl beat cream with an electric mixer on medium to high speed until stiff peaks form (tips stand straight). Gently fold egg mixture into whipped cream; set aside. In a small bowl combine biscotti, almonds, and white chocolate; set aside.
Line a 9x5x3-inch loaf pan with plastic wrap. Spread one-third of the custard in bottom of prepared pan. Freeze for 30 minutes. Top with half of the biscotti mixture. Spread another one-third custard in pan. Freeze for 30 minutes. Top with remaining biscotti mixture. Spread remaining custard in pan. Cover and freeze for 6 to 24 hours.
Meanwhile, for sauce, thaw raspberries, if frozen; do not drain. In a blender or food processor combine the 3 cups raspberries and vinegar. Cover and blend until smooth. Strain berry mixture through a fine-mesh sieve into a bowl; discard seeds. In a small saucepan combine the 1/4 cup sugar and cornstarch. Add strained berry mixture. Cook and stir over medium heat until thickened and bubbly. Cook and stir for 2 minutes more. Transfer to a bowl. Cover and chill for at least 1 hour.
To serve, invert loaf onto a chilled serving platter; remove plastic wrap. Cut into slices; serve on chilled dessert plates with sauce. If desired, garnish with lemon wedges and/or additional fresh raspberries.