
In a medium bowl, whisk together gluten free flour, brown sugar, baking powder, baking soda, salt and xanthan gum (if needed). Set aside for now.
In a large bowl, whisk together the milk, egg, melted butter, and vanilla extract.
Add the dry ingredients into the bowl of the wet ingredients. Stir with a silicone spatula just until combined (don’t overmix).
Let the batter rest (at room temperature) for 20 minutes before moving onto the next steps. This gives the gluten-free flour time to properly absorb the liquid ingredients.
Preheat oven to 350°F (177°C).
Spray a full size donut pan with gluten free non-stick baking spray.
Add the batter to a large food-safe storage bag or piping bag. Seal the bag and cut a corner (or tip if using a piping bag) off.
Squeeze the bag carefully, filling the greased donut pan with batter. Only fill each donut cavity half way full. This donut batter will rise quite a bit and if the donut cavities are overfilled then the donuts will overflow during baking and lose their donut shape.
Bake for 13-15 minutes. The tops should be a light golden brown and a toothpick inserted in a donut should come out clean (no wet batter on the toothpick).
Place the pan on a cooling rack and cool for 5 minutes before removing the donuts from the pan and placing the donuts directly on the cooling rack.
In a medium bowl, stir the glaze ingredients (powdered sugar, milk and vanilla extract) together until smooth.
Dip each warm donut into the glaze and place back on the cooling rack. Dip either just the top of the donut or the entire donut into the glaze. Top the glazed donut with sprinkles (optional).
Place the chocolate chips and coconut oil together in a bowl. Place in microwave, on high heat, for 30 seconds. Remove from microwave, stir, and microwave for an additional 15 seconds. Remove from the microwave and stir again. Repeat this step of heating for an additional 15 seconds followed by stirring until the chocolate is fully melted and smooth.
Dip the donuts in the chocolate glaze, place them on the cooling rack, and add sprinkles, if desired.