Chill a can of coconut milk in the refrigerator overnight. When ready to use, turn can upside-down and open without shaking. Drain of the separated liquids (do not discard, keep for smoothies).
Chill the bowl and whisk of a stand mixer, by placing them in the freezer for three to five minutes.
Add all the ingredients to the chilled bowl and whip on medium-high until firm peaks form.
Fit a piping bag with a plain round tip and transfer the whipped Mascarpone to the bag.
Pipe little balls all around the cake, starting at the edge and tapering off towards the centre. Pipe a second row, staggered from the first in the same manner as the first.
Fill the centre with sprinkles and a Sixlet, or a mini rose.