Place 236g of the steamed sweet potatoes & coconut milk into a blender & blitz till smooth. You can also mash them by hand, but ensure puree is fine.
Preheat oven to 165°C.
Add 150g sugar to a large mixing bowl with the egg yolks, Cocorosco Coconut Oil, sweet potato puree, top flour, baking powder, salt & pandan essence. Whisk to blend thoroughly.
To make meringue, combine the egg whites and cream of tartar in the bowl of an electric mixer & whisk on medium-high speed until frothy. Gradually add the 60g sugar, beating until egg whites are almost stiff.
Scrape half of the egg whites into the sweet potato batter and fold until partially blended. Add remaining egg whites and fold until just incorporated.
Scatter 1.5cm cubes of sweet potato evenly over base of 24cm chiffon tin. Pour in a third of batter to cover the cubes, scatter more cubes over, pour batter. Repeat once more. Smoothen top with spatula.
Bake for 62 – 65 mins, or until the top of the cake is golden brown & a wooden skewer inserted into the center emerges dry, with only a few tiny crumbs clinging to it.
Carefully overturn cake onto a cooling rack & allow to cool completely before unmoulding.
Store cake in airtight container in the fridge for up to 3 days. Bring to room temperature or microwave for several seconds till warm before eating.