1. Dissolve yeast and sugar in 1 cup warm water in a small bowl; let stand 5 minutes. Lightly spoon flour into dry measuring cups, and level with a knife. Combine 1 1/2 cups flour and salt in a large bowl. Add butter, yeast mixture, and remaining 1 1/2 cups flour, stirring until a soft dough forms.
2. Turn dough out onto a lightly floured surface, and knead until smooth and elastic (about 5 minutes). Place dough in a large bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place (85°), free from drafts, 40 minutes or until doubled in size. (Press two fingers into dough. If indentation remains, the dough has risen enough.)
3. Punch dough down; divide into 12 equal portions. Cover and let rest 10 minutes on a lightly floured surface. Shape each portion of dough into an 18-inch rope with tapered ends; twist each rope into a pretzel shape.
4. Preheat oven to 450°.
5. Combine 4 cups water and baking soda in a large nonaluminum Dutch oven; bring to a boil. Add 4 pretzels; cook 1 minute, turning once (do not overcrowd pan). Remove pretzels with a slotted spoon; shake off excess water. Place pretzels on a baking sheet coated with cooking spray; sprinkle 1/4 teaspoon kosher salt evenly over pretzels. Repeat procedure twice with remaining pretzels and salt.
6. Bake pretzels at 450° for 10 minutes or until golden brown. Remove from pans to wire racks.