1 3/4 cups (245 g) all purpose gluten free flour (I used Better Batter)
3/4 teaspoon xanthan gum (omit if your blend already contains it)
3/4 teaspoon baking powder
1/4 teaspoon baking soda
1/2 teaspoon kosher salt
1/4 cup + 1 tablespoon (30 g) peanut butter powder (I used PB2 brand)
6 tablespoons (84 g) unsalted butter, melted and cooled
3/4 cup (150 g) granulated sugar
1 egg (50 g, weighed out of shell), at room temperature
1 teaspoon pure vanilla extract
1/4 cup (64 g) smooth natural peanut butter, warmed slightly
1/3 cup (85 g) sour cream or Greek-style plain yogurt, at room temperature
1/2 cup (4 ounces) semi-sweet chocolate chips
2 ripe bananas (200 g), peeled and mashed very well (from about 2 medium bananas)
Preheat your oven to 350°F. Grease and line a standard 9 x 5-inch loaf pan and set it aside.
In a small bowl, place the flour, xanthan gum, baking powder, baking soda, salt and peanut butter powder, and whisk to combine. Set the dry ingredients aside. In a large bowl, place the butter, sugar, egg, vanilla, peanut butter, and sour cream, and beat with a handheld mixer (or a large fork and some elbow grease) until smooth and well-combined. Add half of the dry ingredients to the bowl, and mix by hand until just combined. Toss about 3 ounces of the chocolate chips in the remaining dry ingredients. To the large bowl, add all of the mashed bananas, and mix, then the remaining dry ingredients and chocolate chips, and mix until just combined. The batter will be thick.
Transfer the batter to the prepared loaf pan and smooth into an even layer with a moistened spatula. Add the reserved chocolate chips to the top of the loaf and press gently to help them adhere to the batter. Place the pan in the center of the preheated oven and bake for 25 minutes, rotate the loaf pan in the oven, and continue to bake until a toothpick comes out mostly clean and the loaf is relatively firm to the touch (another 20 to 25 minutes). Allow the bread to rest in the loaf pan for 10 minutes before transferring to a wire rack to cool completely before slicing thickly and serving.
Any leftover slices can be wrapped tightly and stored at room temperature for 2 days or in the freezer for longer storage. Defrost at room temperature or in the microwave on 50% power.