Bake up a tray of this soul-warming Buttered Rum and Candied Sweet Potato Crumb Cake for your family this weekend! It's gorgeously spiced with cinnamon and clove, and such a perfect start to a crisp fall weekend.
In a medium bowl, whisk together the flour, granulated sugar, brown sugar, and cinnamon.
Slowly whisk in the melted butter, letting it coat the dry ingredients until crumbs are formed. (The mixture will seem wet, but this is normal. Pinch pieces together to form more crumbs.)
Preheat your oven to 350 degrees F, and liberally grease a 9x13-inch baking pan with baking spray.
In the bowl of your stand mixer fitted with the whisk attachment, beat the egg whites on high speed until stiff peaks form.
Transfer the whipped egg whites to a small bowl and place in the refrigerator.
Beat the granulated sugar and oil on medium-high speed until combined.
Add the egg yolks, 1 at a time, combining well after each addition and scraping down the sides and bottom of the bowl as needed.
Add the sweet potatoes, hot water, and vanilla extract, and beat for another 3 to 4 minutes.
Turn your mixer down to its lowest speed and carefully add the flour, baking powder, cinnamon, cloves, salt, baking soda, and nutmeg. Mix the batter until just combined. (Be careful not to overmix.)
Remove the egg whites from the refrigerator and gently fold them into the batter.
Pour 1/2 of the batter into the prepared pan. Cover with 1/2 of the streusel. Repeat with the remaining batter and streusel.
Bake for 55 to 65 minutes, or until a toothpick inserted into the center of the cake comes out moist but mostly clean.
Let cool in the pan for 10 minutes, then poke the top of the cake in various locations with a toothpick.
Lightly cover the cake with foil or plastic wrap so it does not dry out. While the cake continues to cool, prepare the sauce.
In a medium saucepan over medium heat, bring the granulated sugar, butter, rum, and water to a boil.
Whisk until the sauce thickens, about 3 to 5 minutes. When the sauce can thickly coat the back of a spoon, remove from the heat and let cool for 10 to 15 minutes.
*To roast the sweet potatoes: Preheat your oven to 400 degrees F. Prick the sweet potatoes with a fork, then rub each with 1 teaspoon of vegetable oil. Individually wrap each potato in foil and place them all on a baking sheet. Bake for 35 to 55 minutes, or until they are nice and soft. This time will vary based on the size of your sweet potatoes. When you can easily squeeze the sweet potatoes and the insides are tender, they are done.