Heat oil in a large frying pan; cook onion, stirring, until softened. Add washed, drained (not dried) spinach; cook, stirring, until wilted. Remove from heat; when cool enough to handle, squeeze out excess liquid. Combine spinach and herbs in a medium bowl; season.

Preheat oven to 200°C. Line a large oven tray with baking paper.

Sift flours into a large bowl; rub in butter. Stir in half the parmesan. Make a well in the centre; stir in combined buttermilk and egg, mix to a soft, sticky dough.

Knead dough gently on a floured surface until smooth. Press dough into a 20cm x 30cm rectangle. Spread spinach mixture over dough leaving 2cm strip along one long side. Sprinkle remaining parmesan and fetta over spinach. Roll up firmly, from the other long side; place on tray.

Using a sharp knife, cut the top of dough to make eight slices, without cutting all the way through. Brush with a little extra buttermilk.

Bake damper about 40 minutes or until loaf sounds hollow when tapped. Stand damper 30 minutes before serving.