In a large mixing bowl or the bowl of an electric mixer, dissolve the yeast and brown sugar in the 1 1/2 cups warm water. Stir in the flour and salt. Knead on the benchtop or with the dough hook until the dough is soft and elastic, about 8 minutes.
Place the dough into an oiled bowl, and turn the dough to coat the surface with oil. Cover with plastic wrap and then a tea towel, and let rise for one hour in a warm place. The dough will at least double in size.
After dough has risen, divide it into 12 pieces. Roll each piece into a long strand, fold over once and twist to form a knotted roll. Fold over again if you wish.
Combine the 2 cups warm water with the bicarb soda in a bowl. Dip the knotted rolls into the bicarb water mixture and place on the prepared baking tray. Preheat the oven to 230 C (450 F) and allow the pretzel rolls to rise for a further 15 minutes.
Bake for 8 to 10 minutes, or until golden brown. As soon as they come out of the oven, brush with melted butter, and sprinkle with salt flakes.