Add almond flour, xanthan gum, baking soda and salt (omit if using salted butter) to a medium bowl. Whisk until thoroughly combined and set aside.
Cream butter in a large bowl with an electric mixer until light and fluffy, about 3 minutes. Add in a lightly whisked egg, mixing until just incorporated. The mixture will appear slightly 'broken' (i.e. not thoroughly smooth).
With your mixer on low, add in half of your flour mixture- mixing until thoroughly incorporated. Mix in the rest.
Trim the tip of a piping or zip-lock bag (about 1/3" or 1 cm) and transfer your breadstick dough. Pipe out onto a lined baking tray, smoothing away with your fingers any cracks. What worked for me to smooth out some 'rougher' parts here, was to roll it gently against the parchment paper (you know, like play-doh when we were kids!). Place in the fridge to chill for at least 30 minutes.
Preheat oven to 350°F/180°C.
Brush egg wash (I used my finger tips) and sprinkle toppings of choice. Do note that while you can technically skip the egg wash, I did find that they browned *much* nicer with it (i.e. highly suggested if looks are important for you)(and we do eat with our eyes, iykwim).
Bake for 17-20 minutes, or until lightly golden. Remove from oven and allow them to come to room temperature (about 10 minutes), and return to the oven for a second 10 minute bake (we're taking the double bake approach of biscotti here!). Turn the oven off, leave the door slightly ajar (I prop mine open with a kitchen cloth) and let them chill there until the oven comes to room temperature.
Store in an airtight container for up to 5 days.
Notes
The shaped dough can be frozen for up to 3 months, and they can be baked straight from the freezer (adding about 5 minutes more to the baking time).