Mix the brown sugar (½ tsp) into the warm coffee (60ml/¼ cup) to dissolve, then set aside to cool.
In a medium bowl, combine cream (125ml/½ cup), icing sugar (2½ tbsp) and vanilla essence (¼ tsp) and whip into soft peaks, then add mascarpone (250g) and mix to combine.
Into your four serving glasses, spoon a layer of the mascarpone cream into each, roughly smoothing the top as you go.
One at a time, dip four lotus biscuits (we will use 16 in total) into the sweetened coffee, then place on top of mascarpone mixture in each glass. You may need to snap the cookies to fit before you dip them.
Spread the cookie butter (150g/½ cup in total) onto four more lotus biscuits and place these on top of the other cookies in the glasses.
Then add another layer of mascarpone cream and repeat with a layer of coffee-soaked biscuits and cookie buttered biscuits.
Finish with a final layer of mascarpone cream.
Refrigerate for 2-3 hours (or overnight) to set, this allows the biscuits to soften (see my notes) then dust the tops with cocoa powder to serve.