Pour the water into a large bowl and whisk in the yeast. Let it sit for 1 minute, then whisk in the brown sugar, butter and salt. Switch to a rubber spatula and start to add in 3 cups flour, 1 cup at a time. Then add in 3/4 cup more, a 1/4 cup at a time until it's all incorporated. At this point, if the dough is still sticky, continue to add flour a 1/4 cup at a time until it is no longer sticky. The dough should bounce back after you poke it when it's ready to knead.

Turn the dough out onto a floured surface and knead it for 3 minutes, then form it into a ball and cover with a clean towel to let it rest for 10 minutes. While it rests, start heating the water and baking soda in a large pot over medium-high heat. Preheat the oven to 400°F. Line 2 large baking trays with parchment paper or silicone baking mats and set them aside.

Use a sharp knife or a pizza cutter to divide the dough into 12 even 1/3 cup portions. Roll each portion into a rope, about 20-22 inches long. To form the pretzel shape, first make a U shape with the dough. Then cross the ends together in an X. Twist them once and fold it towards you. Press it lightly onto the bottom of the dough rope. Repeat with all dough portions.

Once all of your dough is shaped, your water should be boiling. Working one at a time, use a slotted spatula to gently drop each pretzel into the water and boil for 20 seconds. Then lift it out and allow any excess water to drip off. Place it onto the baking tray (6 to a tray). Repeat the process with each pretzel.

Bake for 7 minutes, then remove the pretzels from the oven and brush them with the melted butter. Sprinkle cinnamon sugar over each and return them to the oven for another 4-8 minutes, or until the pretzels are golden brown. Sprinkle with a bit more cinnamon sugar. Then let them cool slightly before serving. They are best on the day they're made, but you can store them in an airtight container for up to 3 days. I would recommend heating the leftover pretzels before serving.