Make the dough. Put all the ingredients into a large bowl and mix by hand or with a mixer until a soft, smooth and elastic dough forms. If you’re mixing by hand this could take up to 10 minutes, in a mixer it takes around 4-5 minutes.
Place the dough in a clean bowl and use the dough proving setting in your steam oven until the dough has doubled in size, about 30-40 minutes. There’s no need to cover the bowl. If you don’t have a dough proving setting, steam setting at 35°C/95°F (100% humidity) will achieve similar results.
Turn the dough out onto a floured surface and gently press it down to remove any large air pockets (no need to flatten it into submission here!). Divide the dough into 16 pieces and form each into a smooth roll.
Take your string and cut 15 long pieces – I found about 24”/60cm pieces was about right. Put a little vegetable or olive oil on your fingers and run each piece of string over them to lightly grease it. Place a piece of string over the middle of a formed roll then turn it over and cross the string over like you’re wrapping a gift, and turn it back over again. Repeat this so you have 8 sections, then tie the string in a loose knot at the top and trim any excess. You don’t want to pull the string too tight when you’re wrapping it around the dough, as the dough will expand and the shape will be formed during the second prove. Repeat the string tying for each roll.
Place the rolls in a lightly greased or parchment-lined 22cm x 32cm (9in x 13in) pan. Place the pan in your steam oven on dough proving setting again and let the rolls rise until they’re puffed and the dough springs back into shape when a finger is gently pressed onto the surface, about 25-30 minutes.
With the pan still in the oven, change your oven temperature to 180°C/350°F, combination steam setting. If your oven has variable steam levels, select 30% humidity (if you don’t have variable steam settings, don’t worry! Just set the temperature and combination or convection steam, and the oven will work out the rest).
Bake the rolls until they’re golden brown, about 20 minutes, then remove from the oven and turn them onto a rack. If you’d like to give them a gloss, brush each roll with the extra melted butter while hot.
Serve rolls warm or at room temperature. Store any leftovers in an airtight container for a couple of days at room temperature, or freeze for up to 2 months.