Put the coffee into a shallow dish and
dissolve in 150ml boiling water. Set out
4 sundae glasses or teacups. Whisk
together the mascarpone, custard, sugar
and 1 tbsp Marsala, if using, until smooth.
Dip a couple of sponge fingers into the
now cooled coffee for a few secs until
soaked but not soggy, then put into the
bottom of one of the glasses, breaking
them to fit if needed. Repeat, using
enough fingers to make a decent layer
of sponge at the bottom of each glass.
Drizzle with remaining Marsala, if using.