In a large mixing bowl, combine warm water and yeast. When the yeast dissolves, add half of the flour, the butter, salt, and sugar and mix for about 3 minutes. Stir in the remaining flour. Turn dough out onto a floured surface and knead until the dough is no longer sticky. Let the dough rise in a greased, covered bowl until it doubles in size, about 45 to 50 minutes. Punch down the dough and divide into 12 pieces. Roll each piece of dough into 18-inch long ropes. On a greased cookie sheet, shape each rope into a pretzel shape. Let rise again until almost doubled, about 30 minutes.
Preheat oven to 500 degrees F.
In a large non-aluminum Dutch oven over high heat, bring 4 cups of water and baking soda to a boil. Using a large spoon, gently lower pretzels into water a few at a time and boil for about 1 minute, or until they float. Return the pretzels to the cookie sheet and brush with melted butter then sprinkle with kosher salt. Bake until browned, about 12 minutes. Serve hot with mustard.
Recipe courtesy of Paula Deen