Mix the espresso and Marsala wine in a bowl.
Quickly dip half of the sponge fingers into the coffee mixture and layer them in a square dish.
Beat the coffee and vanilla ice creams in separate bowls until smooth.
Spread the softened coffee ice cream over the sponge finger layer.
Dip the remaining sponge fingers in the coffee mixture and layer them over the ice cream.
Spread the softened vanilla ice cream over the top layer.
Dust the surface with cocoa powder and freeze for 20 minutes.
Melt the chocolate pieces and double cream in a bowl over a pan of simmering water.
Stir in the butter until the sauce is glossy and keep it warm.
Serve cake squares garnished with grated chocolate and hot chocolate sauce.