First make the purple yam dough.
Pour the warm water (115 F) in a shallow bowl. Sprinkle yeast on top and wait 5-10 minutes, until foamy.
In the bowl of an electric mixer, combine flour, salt and sugar. Mix to combine.
In a small bowl, whisk together melted butter, coconut milk and purple yam.
Add proofed yeast to flour and knead for a few minutes.
Add coconut milk mixture and knead for 5-10 minutes, until dough is smooth and elastic.
Place in a greased bowl and cover with a kitchen towel for about 1 hour, until doubled in volume.
Repeat same procedure for Sweet Potato Dough.
On a lightly floured surface, roll out purple yam dough to a rectangle approximately 17"x13". Set aside.
On a lightly floured surface, roll out sweet potato dough to a rectangle approximately 17"x13".
Place the purple yam dough on top of the sweet potato dough.
Roll into a tight cylinder.
Slice into 25 pieces.
Prepare a cookie sheet and baking tray with parchment paper.
Place slices on baking trays and cover with a kitchen towel. Leave to rise for 15 minutes.
Preheat oven to 375 F.
Bake for 20-25 minutes until golden and crusty.
As soon as it comes out of the oven, brush with melted butter.