Melt and dissolve butter and sugar with hot water in a mixing bowl.
When the butter and sugar are dissolved, add your sourdough starter.
Gradually mix in 3-4 cups of flour.
Turn out onto a well floured surface.
Knead in the flour and continue adding flour until you have a firm ball of dough.
Place the dough in a well greased bowl.
Put the bowl in a warm place and allow it to rise for 2 hours.
Preheat the oven to 450°F when the dough has risen.
Give the dough a gentle punch down and roll out onto a floured surface.
Knead a few times, and roll out into a log.
Cut into 16 equal pieces.
Roll each piece out into a long, thin piece.
Tie into a knot.
Boil a pot of water and add remaining sugar and baking soda.
Gently lower each pretzel into the boiling water and poach for about 1 minute. You should be able to fit 3 in the pot at the same time.
After a minute, remove the pretzel knots with a slotted spoon and place on a wire rack to dry. Repeat the process with the rest of the pretzel knots.
Brush the tops with beaten egg and sprinkle with salt or other seasonings.
Bake for 15 minutes.