BAKE cookies according to package directions; remove to wire racks to cool completely. Chop cooled cookies into small pieces.
FOR WALNUT MIX:
PREHEAT oven to 375° F. Grease 8-inch-square baking pan.
COMBINE walnuts, butter and brown sugar in small bowl. Pour into prepared pan. Bake for 8 to 10 minutes; stir well. Cool completely in pan on wire rack.
FOR CHOCOLATE SAUCE:
COMBINE evaporated milk, morsels, powdered sugar, Choco Bake and butter in medium, heavy-duty saucepan. Cook over medium-low heat, stirring occasionally, until chocolate is melted. Reduce heat to low; continue cooking, stirring occasionally, for 5 to 7 minutes or until thickened. Remove from heat. Stir in vanilla extract. Cool completely.
WRAP outside of 9- or 10-inch springform pan with foil. Spread 1/3 of crumbled cookies on the bottom of pan. Top with half of the ice cream and half of the chocolate sauce. Combine remaining crumbled cookies and walnut mixture in medium bowl. Spread half of the cookie-walnut mixture over chocolate sauce. Top with remaining ice cream, chocolate sauce (reserving 2 tablespoons) and cookie-walnut mixture.
PLACE remaining 2 tablespoons chocolate sauce in small, heavy-duty plastic bag. Cut a hole in corner of bag; squeeze to drizzle chocolate sauce over top of dessert. Freeze for at least 4 hours or overnight.
TO SERVE, let stand at room temperature for 20 minutes. Remove side of springform pan. Cut into slices.