Preheat oven to 425°F/220°C. Grease and flour (with coconut flour) a donut pan. Alternatively, line a baking tray with parchment paper and draw circles 3 1/2 inches in diameter.
Whisk together in a medium bowl almond flour, coconut flour, psyllium husk and xanthan gum. Set aside.
Heat up water, butter, sweetener and salt in medium pot (or Dutch oven) until it just begins to simmer. Lower heat to low and add in flour mixture, mixing constantly to incorporate. Continue to cook and stir until the dough pulls away from the pan and forms into a ball, 1-3 minutes.
Transfer dough back to the bowl and allow to cool for 5 minutes. The dough should still be warm, but not hot enough to scramble the eggs. And if you have an instant thermometer, temperature should be below 125°F/52°C.
Add in one egg at a time, mixing with an electric mixer at medium/high speed until fully incorporated (if using a stand mixer, use the paddle attachment). Be sure to mix the dough for 2 minutes after adding in the last egg; the final texture should be very elastic. Mix in vanilla extract and baking powder. .
Allow the dough to rest until it comes to room temperature (about 15-20 minutes). I've come to realize this is a very important step to keep your donuts from deflating much post bake; the donuts will rise a bit less but hold their shape better.
Spoon dough into a piping bag or plastic bag (no tip needed). Cut out bottom of piping bag 2 cm (3/4 inch) wide. Pipe out dough onto donut pan, or onto prepared parchment paper (staying within the drawn circle). Wet your finger tip and smooth out where the ends meet (for a more even rise).
Bake for 15 minutes at 425°F/220°C, lower temperature to 350°F/180°C and continue to bake for 17-20 minutes until deep golden. Do not open your oven door before the first 20 minutes (or at all if possible!), as choux pastry is notoriously sensitive to drafts. Allow to rest in pan for 10 minutes before removing. Note: if your donuts are browning too much, feel free to tent them with aluminum foil (just be sure it isn't resting directly over them!).
For the glaze
Sift powdered sweetener and cocoa powder onto a bowl. Add in vanilla extract, butter and milk-of-choice (as needed) until desired consistency is reached. The glaze should be thick, but pourable (I like to use our fingertip here to test for thickness!). Glaze donuts by dunking them onto the glaze (if your tops came out a bit wonky, you can always use the rounder bottoms as your new 'tops'!). Alternatively, feel free to brush with melted butter and sprinkle with cinnamon 'sugar'.
These are best enjoyed still warm and freshly glazed, but they keep quite well for a day or two stored in an airtight container at room temperature.
UPDATE: I've updated the baking temperatures and methodology a tad, and this should keep your donuts from deflatting. But if it happens to you, its generally due to excess liquid (the main reason why baking goods collapse in general). Please note that keto flours vary tremendously from brand to brand, and of course the size of your eggs- so just try using 2 eggs rather than 3!
As many of you seasoned bakers know, the batter for these keto donuts is inspired by a traditional choux pastry. It's light, fluffy, absolutely delicious, and honestly very easy... but it is a bit finicky and known to deflate under certain circumstances, so be sure to check out these tips!
The most common reason for deflating choux pastry is excess liquid. This can come in the form of too large eggs (just try using 2 rather than 3!), be sure you're cooking your dough long enough that it actually forms into a ball (see video), and make sure your oven is calibrated to the correct temperature (or just get a cheap oven thermometer- like most pros do anyways!).
You also want to be sure your dough is below 125°F/52°C before beating in the eggs. It can take anywhere from 5 to 10 minutes, depending on your room temperature. Otherwise you could be curdling your first egg (or two), leading to a lack of structure = deflating donuts.
Allow your final choux dough to come to room temperature before transferring to a piping bag. I've come to realize this is a very important step to keep your donut (holes) from deflating post bake; the donuts will rise a bit less but hold their shape great.
And last, but not least, be gentle! Refrain from opening your oven for the first 20 minutes... and if possible don't open it at all! Definitely be careful to not slam your oven door (I know mine has a tendency to do that), and be gentle when taking them out of the oven. Don't have your A/C blasting, keep doors closed, etc... i.e. ensure there are no drafts!
What to do if yours deflate?! Turn them into French toast (for real!). During my latest experiments to see what was causing the pastry to deflate, I ended up with a lot of 'mistakes'... and it turns out that they make the most delicious French toast bites ever (and you'll come back raving about it either way lol!).Please note that nutrition facts were estimated for the donuts only (so you accommodate for your topping of choice), and we found a batch to yield 8. Still, most toppings add very little (i.e. negligible) carbs.Oh, and apologies for the awkward yield number, but every time I tried to yield 6 it simply didn't work the same.