Start by preparing the bretzels. In a bowl mix the flour, water, milk, butter, and the dry yeast. Work until you get a smooth dough. Cover the bowl with a baking towel and let it rest for 1 hour.
Divide the dough in 10. Roll each piece in to a long sausage about 50 cm long, make it a bit thinner on the edges. Fold each roll in to a big bretzel by first make a big U. Twist the ends and fold them down towards the U and press gently together.
Preheat the oven at 200 degrees Celsius.
Ina big casserole prepare the bath with water, salt and bicarbonate. Let it boil.
Dip gently the bretzels one by one in the water, when they rises to the surface after a few seconds it is time to take them up and let them drain on a paper towel.
Place the bertzels on baking paper on a baking sheet. Brush them gently with some milk and sprinkle the coarse salt.
Place in the middle of the oven for 15 minutes. Take them out and let cool down.