In a small bowl, combine the biscuit mix, walnuts and brown sugar. Cut in butter until mixture resembles coarse crumbs.
Press into an ungreased 13x9-in. baking pan. Bake at 375° until lightly browned, 10-12 minutes. Cool on a wire rack.
In a small bowl, beat cream cheese and 1 cup confectioners' sugar until fluffy. Fold in half of the whipped cream; spread over crust. Stir remaining confectioners' sugar into remaining whipped cream; refrigerate until serving.
In another bowl, whisk milk and pudding mixes for 2 minutes. Let stand until soft-set, about 2 minutes. Spread over cream cheese layer. Cover and refrigerate for at least 4 hours before serving.
Garnish with sweetened whipped cream and, if desired, chocolate curls.