Preheat the oven to 375F.
Prepare two baking pans lined with parchment paper or foil and lightly oil or spray the sheets.
Measure the warm water into a large mixer bowl. Sprinkle the yeast in to the water, whisk with a fork and let it sit for about 5 minutes. Add the flour, sugar and salt and mix until blended, then add the butter in pieces. Mix in a stand mixer with a dough hook for about 2-3 minutes or knead about 5 minutes by hand. The dough should be well blended and slightly sticky but not wet. Cover and let dough rise in a warm place until doubled in bulk, about 1 hour.
Cut the dough into 8-10 equal pieces. Using your hands, roll each piece on the counter to create a rope about 18 inches long. If the dough resists rolling, allow it to rest 5 minutes before proceeding. Shape into a pretzel by forming the dough into a U-shape, crossing the ends twice with the meeting point in the middle, then folding the ends down on to the bottom of the U and pinching into place. Place on the baking sheets, leaving 1½ inch between pretzels. Cover again and let rise for 15 minutes.
In a small bowl, beat the egg with a fork. Brush pretzels lightly with the beaten egg and sprinkle with seeds or kosher salt. Bake for approximately 15 minutes, until golden brown and shiny, rotating pans halfway through baking. These are best enjoyed when freshly made.
