Warm 110ml of the milk in a small saucepan over a low heat to a temperature between 100-115°F (38-46°C).
Pour the warmed milk into a medium-sized mixing jug, then stir in the yeast and honey with a wooden spoon. Allow it to rest for 10-20 minutes or until the surface appears frothy, thick and bubbly.
In a separate large bowl, stir the water and psyllium husk together until well combined. Allow this mixture to stand for 2-4 minutes until it forms a gel-like consistency.
In another separate bowl, whisk together the flours and the salt.
Pour the yeast and milk mixture, flours, cooled melted butter, vanilla, and egg to the bowl with the psyllium gel. Mix everything together for 2-3 minutes with an electric hand whisk or the bowl of a stand mixer. The dough will still look a little sticky.
Using hands floured with potato starch, remove the dough from the bowl and weigh out into 6 x 100g portions.
Roll the dough into balls and place on a baking tray lined with parchment paper. Space them apart and cover them loosely with oiled cling film.
Place the baking tray in a warm space to allow the dough to prove for 45 minutes – 1 hour during which the doughnut balls should have almost doubled in size.