Beat Milo and cream together until stiff peaks form.
Spread 1 side of a biscuit with Milo mixture and sandwich together to another biscuit. Place on a tray. Spread another biscuit with mixture and sandwich to the first 2, and continue with remaining biscuits to create a log shape.
Optional: Dip each biscuit briefly in liqueur or milk before speading with milo mixture.
Using a flat knife, spread remaining milo mixture over log to cover.
Loosely cover with cling wrap and refrigerate overnight to allow biscuits to soften.
Sprinkle log with grated chocolate. To serve, slice on an angle instead of straight across so you can see the layers of biscuit and cream.