Wash the sweet potato thoroughly and peel the potato partially, as shown in the picture. Cut off both ends, wrap with plastic wrap, and microwave until softened enough to mix and mash.
Separate the egg whites and yolks. You'll make a meringue with the whites, so keep in the refrigerator until use.
Bring the butter to room temperature. Sift together the ☆ cake flour and cinnamon. Preheat the oven to 180℃.
Mash and stir the softened sweet potato to your desired texture. Add the heavy cream, condensed milk, and honey. Mash it all together.
Using a wooden spatula, mix the softened butter until fluffy. When it becomes white and fluffy, add the caster sugar and mix with a hand mixer or whisk. Keep mixing until the texture of the sugar becomes fluffy and no longer coarse. Add the beaten room temperature egg yolk a little at a time and mix with each addition.
Add the mixture from Step 4 to the bowl from Step 5 and combine with a spatula.
Make the meringue. Add a pinch of salt (not listed) into the chilled egg whites. Beat with a hand mixer. Mix in the sugar a little at a time until firm peaks form. Divide the meringue in half and mix one half at a time into Step 6.
Lightly oil the pan and line with parchment paper. When the meringue is completely mixed into the batter, add the ☆ ingredients a little at a time and mix until thoroughly combined. Once mixed, pour into the pan. Create a long well in the center.
Bake at 180℃ for 50~55 minutes. It has a lot of moisture, so it might not look done, but if you stick a toothpick or skewer in the middle and it comes out clean, it's ready. It's kind of heavy, so it's like eating a Japanese sweet ♪
Story Behind this Recipe
This is a recipe using purple sweet potatoes. If you like a little more spice, increasing the cinnamon to 4 grams. Make this when sweet potatoes are in season~♪ For regular sweet potatoes, test it out without cinnamon first. (^_-)-☆ Purple sweet potatoes have an interesting color, so it'll become an interesting treat!
If you reduce the amount of sweet potatoes, increase the flour by 20% and add baking powder, it will have the texture of a regular pound cake. If you let it sit for a day, the flavor is really melt-in-your-mouth delicious~♪ This is a pound cake you'll want to eat enjoy with a strong brew of black tea.