PREHEAT oven to 350° F. Grease and line bottom of two 8-inch-square cake pans with parchment paper.
COMBINE flour, sugar, baking cocoa, baking soda and salt in large mixer bowl. Beat in sour cream, butter, eggs and vanilla extract until just moistened. Beat on medium speed for 3 to 4 minutes or until light in color. Spoon into prepared pans.
BAKE for 40 to 45 minutes or until wooden pick inserted in center comes out clean. Cool in pans on wire racks for 10 minutes; remove to wire racks to cool completely.
MICROWAVE morsels in microwave-safe bowl on HIGH (100%) power for 1 Minute; STIR. Morsels may retain some of their shape. If necessary, microwave at additional 10- to 15-second intervals, stirring until smooth.
COMBINE pudding mix and milk in large mixer bowl. Beat for 2 minutes or until thickened. Beat in cream cheese. Fold in whipped topping. Fold in 3 cups marshmallows.
SLICE each cake layer in half horizontally. Place two layers, side-by-side, cut-side-down on large serving platter. Spread 1/2 the melted chocolate over the cake layers. Lightly press half the graham crackers into melted chocolate, cutting crackers to fit. Spread 1/2 the filling over graham crackers. Repeat with remaining cake layers, melted chocolate, graham crackers and filling, covering tops only, not sides of cake.
COARSELY chop chocolate covered graham crackers. Sprinkle over top of torte. Sprinkle with remaining marshmallows. Refrigerate for at least 5 hours or overnight.