Combine dry ingredients in a mixer bowl fitted with a dough hook.
Add oil, treacle, walnuts, and 250ml tepid water while kneading on slow speed.
Add up to 100ml more water gradually to create a soft dough.
Knead on slow speed for two minutes, then medium speed for four minutes.
Knead by hand on a floured surface until smooth and pliable.
Place in an oiled bowl, cover, and prove for one hour until doubled.
Knock back the dough and set aside 200g.
Flatten the larger portion into a 30cm circle on a lined tray.
Place a 7.5cm cutter in the center and cut 16 segments around the edge.
Twist each segment 90 degrees and shape the removed center circle into a ball.
Roll the reserved 200g of dough into two circles and cut each into eight triangles.
Place triangle bases in the central hole and fold points inward to form inner petals.
Place the dough ball in the center, cover, and prove until doubled.
Preheat the oven to 210°C.
Brush inner petals with egg and dust outer petals with flour.
Score the central ball with a sharp knife and bake for 30-35 minutes.