i bought some really beautiful purple sweet potatoes during the weekend and immediately set my eyes on this. i've seen this on several blogs and the violet amethyst-like cubes embedded within the cake really caught my attention. i guess i just hv this weakness for pretty desserts (and purple sweet potatoes).
the cake turned out fluffier than i thought, consider that the purple sweet potato puree was rather thick and heavy. tastewise its pretty mild since the sweet potato doesn't really hv much taste/aroma to begin with but i do like the subtle sweetness and the contrast of the cubes with the cake. i also think that its better eaten fresh from the oven coz that raw eggy smell will be more apparent upon cooling.
recipe is adapted from here and the original yields a 17cm cake but i scaled it up since i only hv a 22cm tin. also, i don't like the idea of using cream of tartar when whisking egg whites coz i don't see a difference in the results. japanese pastry chefs don't use it in their recipes either so i'll usually omit. sugar and egg whites alone will give you a beautiful meringue so you don't need cream of tartar, or vinegar, or lemon juice.