Combine the water, sugar and yeast in the bowl of a stand mixer. Allow to stand for 5 minutes until foamy.
Add the flour and salt and allow to knead with the dough hook until the dough starts coming together.
Add the butter, one tablespoon at a time, and allow to knead in. Knead the dough on low speed for 5 minutes.
The dough will be soft, slightly sticky and smooth. Cover and allow to rise for 1 hour (or cover with plastic and allow to rise overnight in the fridge).
In a pot or Dutch oven set over medium high heat, melt the sugar, butter, syrup and salt together.
Allow to cook until golden brown and smooth. Pour into the bottom of a casserole dish (32cm/13inch) then add the walnuts.
Combine the brown sugar, cinnamon, salt and melted butter together.
Once the dough has risen, turn it out onto a lightly floured surface and roll out into a rectangle. The dough should be approximately 1cm thick.
Spread the filling onto the dough then roll into a tight roll. Using a sharp knife (or dental floss - this is the BEST trick to get clean slices through the dough), cut the dough into 8 large (or 12 medium) buns.
Place the buns on top of the caramel then cover and allow to proof for 30 minutes in a warm spot while you preheat the oven.
Preheat the oven to 180ºC/350ºF then place the buns in the oven.
Allow to bake for 20-25 minutes until risen and golden brown on top. Remove from the oven then carefully invert onto a cooling rack and allow to cool for 10 minutes before serving.