Preheat your oven to 400°F. Grease or line a 10- x 15- x 1-inch jelly roll pan with parchment paper, and set it aside.
Place all of the dry ingredients (flour, xanthan gum, baking powder, bakign soda, salt, and sugar) in a large bowl and whisk to combine well.
If you’re using a store-bought pancake mix, measure out 345 grams of the mixture by weight.
Create a well in the center of the dry ingredients, and add the milk, beaten eggs, and melted butter to the center.
Whisk or mix vigorously to combine. The batter will be thickly pourable.
Pour the batter into the prepared pan and rotate it a bit so the mixture is in a single, even layer.
(Optional step) Scatter a small handful of blueberries and raspberries evenly over the top of the batter in the pan. There should be large gaps between the berries.
Place the pan in the center of the preheated oven and bake until puffed and beginning to brown on the edges (about 18 minutes). A toothpick inserted in the center should come out mostly clean (a few moist crumbs are fine).
Remove from the oven, and allow to cool in the pan for about only a couple minutes before slicing into squares and serving.
Video
Notes
About xanthan gum & the amount of milk.If you don’t use the optional xanthan gum in the dry pancake mix, or you’re using a packaged mix that doesn’t contain xanthan gum, you should only use 1 2/3 cup (13 1/4 fluid ounces) of milk.For the flour if you're not gluten free.Whole wheat pastry flour works in exactly the same way in this recipe as my gum-free gluten free flour blend (or Nicole's Best), plus the added xanthan gum. You don't have to change a thing to make the pancakes that way.If you'd like even fluffier wheat-based pancakes, you can use regular whole wheat flour. You'll need to increase the milk to 2 1/4 cups (18 fluid ounces). That makes fluffier whole wheat pancakes than using whole wheat pastry flour.Nutritional information.Nutrition information is per serving using the gluten free flour blend, assuming 6 servings, and is an estimate only from online calculators and excludes any added berries. It should not be relied upon.