Anyone familiar with using puree'd sweet potato in a Thai Red Curry sauce?

I eat at this Thai restaurant and order the most amazing Thai Red Curry Beef. It has sweet potato, basil, red capsi and has a lovely sweet creamy flavour. The sauce is quite thick and orange coloured, i would swear they have pureed/processed sweet potato to make up that consitency. Anyone know if that is common to use a sweet potato in a thai red curry...and any recipes out there? I would prefer it if its a recipe you use yourself and have tested. I may be wrong about this sweet potato thing but i think i am right.