Preheat the oven to 175°F (80°C). (*Yes, that's 175°F/80°C not 350°F/180°C. The low starting temperature gives the bread a little rising before you hit it with the heat).
Spray a large baking tray with cooking oil spray or line with ovenproof parchment paper and set aside.
Place the dry yeast in a small bowl and pour the 1/3 cup of warm water slowly over it. Mix gently with a fork and set aside for 5 minutes.
Place the sugar, salt and butter into a large mixing bowl. Pour over the boiling water and stir until the butter has melted. Add the cold water and stir. Add the yeast mixture and stir again to blend.
Add half the flour to the bowl and stir, using a wooden spoon, until the dry is incorporated into the wet. Then add enough of the remaining flour until a soft dough forms – I added and stirred in 5 cups of the flour, using the 6th cup to flour the work surface and dough as I kneaded by hand, thus incorporating the last cup little by little until the dough was soft, supple, elastic and no longer stuck to either the work surface or the cutting board. Knead this way, adding in that last cup of flour gradually, for about 6 minutes. Leave the dough to rest for 5 minutes.
Turn the dough out onto the prepared baking tray and divide it into three equal portions. Let the dough rest for another 5 minutes.
Using your fingertips, spread each portion of dough out into a rectangle. Roll each rectangle up like a Swiss roll length ways and then tuck the two ends underneath. Place each rolled loaf on the baking sheet seam side down and gently even out each "log" or loaf.
Spray a sharp knife with cooking oil spray (or rub with vegetable or olive oil) and make three deepish, diagonal slashes into the tops of each loaf.
Brush with the beaten egg and bake at 175°F (80°C) for 15 minutes (*See first instruction step above).
After 15 minutes, INCREASE the oven temperature to 400°F (200°C) and bake for a further 15 - 20 minutes.
Now DECREASE the oven temperature down to 350°F (180°C) and bake for a further 10 - 15 minutes or until the tops are golden, the bottom of the loaves are colored, and the bread sound hollow when knocked.
Transfer the loaves to a wire rack to cool (a little) before slicing.