Add your dry ingredients to a bowl and whisk the ingredients to blend them. Add the 5 TBSP of cold butter.
Use a pastry blender to cut in the butter into the flour. Many wonder if they can use a food processor to cut the butter in. I find a food processor overmixes the butter in and you lose some of the flaky layers. Cutting in the cold butter is what helps make the flaky layers!
Add the milk and mix into a nice dough ball. It should be wet, but workable.
Preheat your oven to 425º F.
Put the dough on wax paper. Depending on the gluten free flour blend you used, you may want to dust the wax paper with a tiny bit of gluten free flour. It depends on which gluten free flour blend you use. Press to 1 ½ inch thickness. (Dust the top of the biscuit dough with a small amount of gluten fre flour as needed.
Use a biscuit cutter to cut out biscuit shapes from the dough. If you prefer, you can use a large ice cream scoop or cookie scoop to make drop style biscuits.
Brush the top of each biscuit with milk. This will help your biscuits get that nice golden color on top.
Bake at 425º F for 15 minutes.
In my test, I tested the following gluten free flour blends: Cup4Cup, Better Batter Artisinal Gum Free Blend, King Arthur Measure for Measure, Bob's Red Mill 1 to 1 Gluten Free Blend, and Just About Food Gluten Free Whole Grain Flour (DON'T use this one blend, it was horrible!)
If your blend doesn't contain xanthan gum or psyllium husk as a binder, you need to add 1 tsp xanthan gum.
You need to use VERY cold butter.
This recipe calls for 2 TBSP of baking powder. Be sure to use aluminum-free baking powder. Regular aluminum baking powder will leave a metallic aftertaste. I used Thrive Market Aluminum-Free Baking Powder. Other brands of gluten free baking powder without aluminum include Rumford, Argo, and Bakewell Cream. You can also make your own DIY gluten free baking powder by mixing 1 teaspoon baking soda, 2 teaspoons cream of tartar, and 1 teaspoon cornstarch.
If you want to make this dairy-free, use non-flavored/sweetened dairy-free milk and vegan butter.
Each brand is a little different. Better Batter I needed to add 2 TBSP of milk to the biscuit batter.
If you prefer to use buttermilk, you can, or add 1 TBSP of lemon juice to your milk.
These biscuits will keep up to 3 days in an air-tight container, or up to 4 months in the freezer.