Preparation:

1)Combine the two flours, yeast and salt in a large bowl, or the bowl of a mixer with a dough hook. Trickle in the oil and then the water, bringing the mix together into a rough dough with your hand, or with the dough hook on a slow speed, as you do so. 2)Tip the dough onto a lightly oiled surface and knead for 5-10 minutes, until smooth - or knead for a few minutes in the mixer. Transfer to a lightly oiled bowl, cover with a tea towel and leave to rise for about 1 hour or until roughly doubled in size. 3)Meanwhile, make the filling. Heat the olive oil in a large frying pan. Add the onion, garlic and a pinch of salt and pepper, and sauté gently for 12-15 minutes, until soft. Add the pear, and the thyme if using, and cook for a further 5 minutes or so, stirring often. Transfer to a bowl or plate and leave to cool. 4)Have ready a baking tin, about 20 x 25cm, lined with baking parchment. Tip the risen dough out onto a floured surface and roll/press it out to a rectangle about 45 x 30cm. Spread the cooled pear filling over the dough, leaving a 2cm border at the long edge furthest from you. 5)Tear the ham into small pieces and arrange over the pear mix. Scatter the grated cheese over this. Starting at the long edge nearest you, roll up the dough like a swiss roll, encasing the filling. Trim off each end (you can squish these bits together to make an extra bun). Cut the long sausage of dough into 12 equal slices, turn them on their sides so that their spiral sides are uppermost and tuck them into the prepared tin. Cover lightly with a tea towel and leave to prove for a further 45 minutes. 6)Preheat the oven to 200°C/gas 6. Brush the proved buns with a little milk and scatter with sesame and black onion seeds. Bake for about 25 minutes until risen and golden brown. Leave to cool a little in the tin, and serve while still just warm.