Combine all ingredients except for the butter in the bowl of a stand mixer fitted with the dough hook.

Mix on medium-low speed for 10-12 minutes until a stiff, smooth dough forms. It will be quite firm - this is fine and is what gives lovely chewy pretzels. Don't freak out.

Add the butter and mix for a further 5 minutes until it is completely incorporated and passes the window pane test.

Shape the dough into a ball, and transfer to a lightly oiled bowl. Cover with plastic wrap and leave in a warm spot for 45 minutes to an hour, or until doubled in size. This initial rise can also be done in the fridge overnight.

Turn the dough out onto a work surface (do not flour), and weigh the dough then divide into 6 equal sized balls. Using slightly oiled hands, shape each into a ball, then place on the bench under plastic wrap to rest for about five minutes.

Line a sheet pan with a silicone baking mat or parchment paper (if you use parchment paper you will need to drain the buns well after their baking soda bath to ensure that they do not stick.

Give each bun a quick re shape and arrange evenly spaced on the sheet pan.

Rise the buns, uncovered, at room temperature for 30 minutes, or until the dough leaves an indentation that springs back slightly when lightly pressed with a fingertip. Transfer the buns to the fridge for 10 minutes.

While the pretzel buns are rising, preheat the oven to 425°f / 220˚c. In a large, shallow pan (I used a frying pan / skillet), combine ¼ cup baked baking soda and 6 cups of cold water. Heat until the solution is steaming, then turn off.

Working with one roll at a time, carefully lift off the baking sheet, and place upside down in the solution. Soak for 10 seconds, then carefully flip over and soak for another. Remove using a slotted spoon or spatula or another flat utensil, and place onto the silicone mat lined baking sheet.

Repeat the process with the remaining rolls.

Carefully brush egg wash over the buns, then snip a cross into them using sharp kitchen scissors - make one vertical cut, then two horizontal cuts, one each side of the vertical one to keep the cross neat. Alternatively you can score with a razor blade or a very sharp knife.

Sprinkle with pretzel salt or flaky sea salt.

Bake the buns for 18-20 minutes, or until deeply golden brown. Remove from the oven and allow to stand for 5-10 minutes on the pan before transferring to a wire rack and allowing to cool completely.

Store leftovers in an airtight container at room temperature. If you are planning to freeze the buns or eat them the next day, leave off the salt before baking as it will make the rolls soggy when stored.