First things first get your oven preheated to 375°F.
Wash your sweet potato, give it a few pokes with a fork, and pop it right on the oven rack (no pan needed). Bake until it’s fork-tender. This usually takes about 40-45 minutes, depending on the size of your potato.Pro tip: If you’re in a rush, you can microwave the sweet potato (poke it a few times and microwave on high for about 6-8 minutes), but I love the caramelized flavor that roasting brings out. Let it cool, then peel and mash it until smooth. Set aside.
While the sweet potato cools, line a loaf pan with parchment paper and lightly grease it. In a large mixing bowl, beat together the butter and sugar until creamy and light. (If your butter’s a little cold, cut it into cubes first it’ll mix easier.)
Add in the egg and mashed sweet potato. Mix until smooth and well combined. In a separate bowl, whisk together the flour, baking powder, and baking soda.
Gradually add the dry ingredients into the sweet potato mixture, stirring just until combined. Don’t overmix it should be thick but light and a little sticky.
Fold in your chocolate drops and chopped walnuts.
Pour the batter into your prepared loaf pan, smoothing the top with a spatula.
Bake at 375°F for 25–30 minutes, or until a toothpick inserted into the center comes out clean.
While that bakes, go ahead and start on the meringue topping.
Grab a clean bowl (and I mean squeaky clean any grease or yolk and your egg whites won’t whip properly). Add the egg whites, powdered sugar, and pinch of salt.
Using a hand mixer or stand mixer, beat the mixture until it becomes glossy and holds stiff peaks. This takes about 5-6 minutes. You’ll know it’s ready when you lift the beaters and the peaks stand up proudly without flopping over.
Once your loaf is done baking, let it cool in the pan for about 10 minutes. This is just enough time for it to firm up a bit but still be warm enough to welcome that dreamy topping.
Gently spread the meringue over the top of the loaf.
Pop it back in the oven for another 6–7 minutes, just until the meringue is lightly golden and kissed with a little crisp on top.
Remove from the oven and let cool another 10 minutes in the pan, then transfer to a wire rack to cool completely.
