The best way to cook sweet potatoes for recipes like this is to bake them. The flesh will shrink away from the skin, and the reduction of the original raw volume will sweeten and intensify the flavour of the sweet potato. This also reduces the amount of water in the potato, so you can get away with using only a little xanthan gum to help the finished texture.
About 7 oz. sweet potatoes
2 large eggs, at room temperature
2/3 cup superfine sugar
1-1/2 cups Gluten-Free Flour Mix (see below)
2 tsp baking powder
1/2 tsp xanthan gum
2/3 cup mild olive oil
1 tsp glycerin
2 tbsp each of bittersweet and white chocolate
Gluten-Free Flour Mix (makes 7-1/4 cups)*
5-1/4 fine white rice flour
1 cup potato flour
1 cup tapioca flour
* Mix all the flours together and store in an airtight container. This mix works well for cookies and cakes.
Step 1: Preheat the oven to 325°F. Place 12 paper muffin liners in a muffin pan.
Step 2: Bake the sweet potato for 50 minutes, until soft. Cool slightly, then peel and mash with a fork. Set the potato aside to cool completely.
Step 3: Increase the oven temperature to 350°F.
Step 4: Place the eggs and sugar in a stand mixer, and beat on high speed until thick and foamy, about 5 minutes. Place the flour, baking powder, and xanthan gum in a separate bowl, and mix well. Whisk the oil and glycerin together in a small bowl.
Step 5: Add the sweet potato flesh to the flour mixture, and chop through with a spoon or fork, breaking it up so the mixture is roughly combined. Roughly chop the bittersweet and white chocolate, and stir into the mixture.
Step 6: Add the oil mix to the eggs, along with the flour and sweet potato; mix well, but lightly.
Step 7: Spoon the mixture into the muffin liners and bake for 20 minutes, or until well risen and lightly browned.
Step 8: Remove the muffin pan from the oven, and let cool on a wire rack.
Reprinted with permission from Phil Vickery's Gluten-Free Baking (2011 Firefly Books).