Place coconut milk in the refrigerator overnight. The next day chill a large glass bowl in the freezer for 15-20 minutes.
Remove the bowl from the freezer and add in milk *, vanilla powder, sugar and whipped cream stabilizer. Whip the cream for 5-10 minutes until stiff peaks form. Cover the bowl with plastic wrap and refrigerate for at least 4 hours before frosting the cake.
For the pumpkin sheet cake
Preheat the oven to 180 degrees (360 F).
Use a mixer and beat aquafaba until it starts to get foamy. Add in sugar and continue to mix until it becomes very fluffy and forms stiff peaks.
Start adding the previously sifted flour, baking powder, cinnamon, salt and baking soda. Mix slowly using a spatula until you get a lump-free mass.
Then add the pumpkin puree and mix gently until well incorporated.
With the help of a spatula spread the mass on a baking sheet lined with baking paper giving it the shape of a rectangle of about 30 X 35 cm with a thickness of 0.5 cm.
Bake in the center of the oven for about 10-15 minutes.
As soon as you pull the sheet cake out of the oven, turn it out onto a clean towel dusted with powdered sugar. Peel off the baking paper and roll the cake up into the towel (starting at one of the short ends). Let cool completely.
Unroll the cake and spread the coconut whipped cream across the cake, leaving about 2 cm (⅔ an inch) around the edge unfrosted.
Roll the cake up and set it in the fridge for at least 4 hours before serving.
*If you use canned coconut milk: open your can of coconut milk and scoop out the hardened coconut cream with a spoon into your bowl and use the remaining liquid to make a smoothie.