Combine the flour, yeast, butter and salt in a large bowl. Mix well, then gradually pour in the cold water, mixing until the dough begins to come together. The dough should be moist but firm enough that you can knead with your hands.

Turn out the dough onto a well floured surface and knead for 15 minutes until smooth and elastic. Form into a ball and return the bowl.

Cover the bowl with plastic wrap or a damp tea towel and let the dough rest for 30-45 minutes.

Remove from bowl to a floured working surface and divide into 8 equal sized pieces. Form each into a small round roll. To form into rolls, repeatedly fold over the outer edges of the ball into towards the center of the ball, gently pressing down. Once the bottom side is round and smooth, turn it over so the smooth side is on top.

Line a baking sheet with parchment paper and evenly arrange the rolls. Lightly cover with a clean tea towel or baking cloth.

Let rest in the refrigerator 8 hours. This helps the outer skin of the dough slightly dry out so it doesn't lose shape when boiling.

While the oven is preheating, prepare the baking soda bath to boil pretzels: Bring 1 liter/1 quart of water to a boil and add 5 teaspoons of baking soda (the ratio of water to baking soda is important! It's what gives the pretzels their distinct color and flavor).

Plop the pretzel rolls into the water 1 or 2 at a time. You don't want to crowd them. Boil for 30 seconds on one side then flip over and boil for another 30-45 seconds.

Remove the boiled pretzels from the pot with a slotted spoon and place on a rack to drain for a couple minutes.

While the pretzels are still wet, cut a shallow "X" shape across the top of each rolls and sprinkle with coarse salt, poppy seeds and/or sesame seeds.

Arrange the rolls on a baking sheet that has been lightly greased or covered with parchment paper.

Bake in the oven at 210°C/410°F. for 18-20 minutes, or until they pretzels turn a deep, golden brown color.