In bowl combine your water and sugar.
Add your yeast and let proof for about 5 minutes until bubbly and foamy.
Add in your salt, butter and flour one cup at a time until it starts to pull away from bowl.
Turn out onto floured surface and knead dough for about 5-7 minutes or until a round smooth ball forms.
Place in greased bowl and set in warm place to rise for about an hour.
Preheat oven to 450.
Once risen, turn out onto greased counter top and separate into 8 equal pieces.
Stretch each piece to about 24" long and flatten with the palm of your hand.
Add some of the filling up the center of each dough piece.
Pinch the sides closed, sealing in the filling and then twist into a pretzel shape.
In large pan combine your water and baking soda.
Add pretzels in batches, about 2 a piece and boil for about 30 seconds.
Remove from pot with slotted spoon and place on greased baking sheet.
After all are done boiling mix together your egg yolk and water and brush over each pretzel and sprinkle with sea salt.
Bake for about 10-12 minutes or until golden.
Sprinkle with additional salt if desired.