Gluten Free Blueberry Swirl Muffins
2 cups (300 g) fresh or frozen blueberries
3/4 cup (150 g) granulated sugar
2 tablespoons (1 fluid ounce) lukewarm water
1 3/4 cups (245 g) basic gum-free gluten free flour blend (162 g superfine white rice flour + 54 g potato starch + 29 g tapioca starch/flour)
1/2 teaspoon xanthan gum
1/4 cup (36 g) cornstarch (or try arrowroot)
1 teaspoon baking powder
1/4 teaspoon baking soda
1/2 teaspoon kosher salt
8 tablespoons (112 g) unsalted butter, at room temperature
2 eggs (100 g, weighed out of shell) at room temperature, beaten
1 teaspoon pure vanilla extract
1 cup (8 fluid ounces) buttermilk, at room temperature
Preheat your oven to 350°F. Grease or line the wells of a standard 12-cup muffin tin and set the tin aside.
In a small, heavy-bottom saucepan, place 1 cup (150 g) blueberries, 1 tablespoon of the granulated sugar and the water, and mix to combine. Cook over medium heat, stirring frequently to break up the berries, until the mixture is thickened and reduced, and all the berries are crushed (about 5 minutes). Set the blueberry compote aside to cool.
In a medium-size bowl, place the flour blend, xanthan gum, cornstarch, baking powder, baking soda and salt, and whisk to combine well. In a separate, large bowl, place the butter and remaining granulated sugar, and using a handheld mixer, beat until light and fluffy. Add the eggs and vanilla, and beat until well-combined. Toss the remaining 1 cup blueberries in about 1 teaspoon of the dry ingredients, and set aside. To the butter mixture, add the remaining dry ingredients in 4 batches and the buttermilk in 3 batches, alternating between the two and beginning and ending with the dry ingredients, mixing until just combined after each addition. The batter should be thick but soft. Fold the blueberries and reserved dry ingredients into the batter until they’re evenly distributed throughout, taking care not to break the berries.
Divide the batter evenly among the prepared wells of the muffin tin. The wells will be almost completely full. Divide the cooled blueberry compote evenly among the tops of the batter in the wells and swirl it into the top of the batter with a toothpick. Shake the pan back and forth to distribute the batter evenly in the wells.
Place in the center of the preheated oven and bake until the muffins are puffed and very, very pale golden, firm to the touch and a toothpick inserted in the center comes out with no more than a few moist crumbs attached (about 20 minutes). Remove from the oven and allow to cool in the tin for 5 minutes before transferring to a wire rack to cool completely before serving.