Mix the espresso powder with the boiling water and caster sugar. Pour into a wide, shallow dish and leave to cool whilst you make the cream filling.
Beat together the cream cheese with the vanilla extract, rum and icing sugar.
Whip the dairy-free double cream until it forms stiff peaks.
Fold the whipped cream into the cream cheese mixture.
Take four equally sized glasses approx 8cm tall and 7cm in diameter. Cut your Madeira cake into 8 slices - each about 2cm thick - and cut around the rim of a glass to shape each slice into a circle that will fit snuggly inside a glass.
Dip a slice in the cooled espresso and place into one of the glasses. Spoon an even layer of the cream mixture on top until the glass is about half full. You can use a paper towel to wipe any excess cream from the inside of the glass.
Dip another cake slice in the espresso and place on top. Then add a final cream layer before dusting with cocoa powder.
Repeat to fill the other three glasses.
Leave your tiramisu pots in the fridge for at least 4 hours before eating, to allow all the flavours to come together.