Line two large baking sheets with baking parchment paper.
Heat the milk to between 38-46°C (100-115°F) in a small saucepan. Then pour into a medium sized glass bowl and stir in the yeast and 2 teaspoons of the brown sugar. Rest for at least 15 minutes until the surface is looking thick and bubbly.
Melt the butter in a small saucepan, then set aside to cool slightly, transferring 2 teaspoons into a small bowl for the egg wash later.
Stir the water and psyllium husk together in a large sized mixing bowl until combined. Allow to stand for about 5 minutes until it forms a gel.
Whisk the sorghum flour together with the rice flour, tapioca flour, rest of the brown sugar and salt in a large mixing bowl.
Combine the yeast and milk mixture, melted butter, psyllium husk gel, flour mixture and the whisked eggs in a large mixing bowl or bowl of a stand mixer.
Beat these ingredients together for 5 minutes until the dough is well combined. It will still be very sticky to the touch.
Dust hands with a little of the extra tapioca flour and pinch some of the dough out of the mixer.
Weigh the dough – it needs to be about 115g.
Place the dough on a work surface, dusted with a little of the extra tapioca flour. The dough will pick up some of the tapioca flour and then roll it out between your hands until smooth, you can also use a clean work surface to get a very smooth surface to your dough ball. Place it immediately onto one of the lined baking trays.
Divide the rest of the dough and roll in the same way. You should end up with 8 balls of dough of 115g each.
Place them 2-3 inches apart divided across the two lined baking tray, four buns to each tray.
Place the trays somewhere damp and warm to prove for 30 minutes (see notes on proving) until the dough balls have increased significantly in sized.
Whilst the dough is proving pre-heat the oven to 190°C / 170°C fan assisted / gas mark 5 / 375°F.
Once the rolls have finished proving then brush the surface of each of the rolls with the extra whisked egg mixed with the 2 teaspoons melted butter. Scatter the sesame seeds over each bun.
Place in the middle of the oven to bake for 15 minutes. The buns are baked when just turning golden brown.
Remove from the oven and cool the buns on a wire rack. Allow to cool completely before serving.