Heat the oil in a frying pan. Add the garlic onion and a good pinch of salt. Cook for 3-4 minutes then add to a mixing bowl and allow to cool. Add the remaining filling ingredients to the bowl and mix well to combine. Place in the fridge.
For the pastry, place the flour in the fridge overnight. Mix the flour with the xanthan gum, baking powder and salt. Cut the butter into small pieces and add to the flour. Now either use a food processor or your fingers and process or rub the mixture so some becomes breadcrumb like but keep some streaks of butter in there.
Now add the egg and water a little at a time and quickly knead the dough to bring it together into a ball. If a bit too wet, add a little more flour.
Now flatten and shape the dough and roll into a fairly even rectangle, fold in half, rotate one turn clockwise and roll out one more time then fold in half and gently roll just to press together ( you still want a square shape). Wrap this and place in the fridge for 1 hour or overnight.
Cut the pastry in half and each piece into 2 rectangle sheets approx.. 15cm wide and 20cm long.
Divide the mince and shape into a long log down the middle
Of each piece of pastry. Brush one edge of the pastry with egg and roll up, sealing on the edge with the egg wash. Make this the bottom. Brush the pastry with egg wash and sprinkle on the sesame seed. Refrigerate each roll for at least an hour to firm up then cut them into what ever size lengths you want. Cook in a preheated 180C oven for 25-30 minutes. Allow to cool slightly then serve with your favourite sauce or mustard if desired.