~ Japanese Sweet Potato Shortbread Cookies

Taken from:
Cakepia

Description:
Shortbread cookies with a sweetness of Japanese potatoes~

Ingredients:

250 g Japanese sweet potato
30 g butter
20 g sugar

1/2 (20 g) egg, whisked
50 g flour, sifted

Directions

1) Wrap a wet kitchen towel over the sweet potato, and followed by a plastic wrap. Microwave on high for 7 min till the sweet potato is soft. While warm, press the sweet potato through a sieve and retrieve 100 g of sieved sweet potato.
2) Cream butter and sugar.
3) Stir in sweet potato and egg till well-blended.
4) Incorporate flour till there is no white specks left, and wrap the dough in a plastic wrap to be refrigerated for at least 1 hour.
5) Slice or cut into desired shape. Brush shaped cookie dough with egg. Bake in preheated over at 180 deg for 15 - 20 min till golden brown. Cool before storing.

Remarks:
Leftover ingredients in the kitchen pose a great temptation to me, for I'll definitely think of ways to use them up! Take for instance in this case, Mum left 2 purple sweet potatoes hanging around in the kitchen and not long after, they appeared somewhat different:

As I didn't know the recipe was for shortbread cookies at first, I baked the nuggets till brown and baked them further till they were no longer soft in the middle. It is only when I was blogging then I realised my folly ops.

Anyway, I was quite surprised that the cookies came out with a nice brown sheen over them (it's not oil). And during baking, the whole kitchen smelt like condensed milk, which was pretty odd since there wasn't even milk added into the dough. I guess it's probably due to the caramelization of the natural sugars in sweet potato and reaction with the butter.

Each cookie is one tough cookie! It was hard to bite through, and once you do, a milky flavour fills the entire mouth. Seriously, where did that milk come from?