Preheat the oven to 220C/425F/Gas 7.
Place the flour, salt, caster sugar and yeast in a bowl and mix.
Create a well in the middle and add 300ml/10fl oz warm water and 100ml/3½fl oz olive oil. Bring the mixture together to a soft dough and turn out on a floured surface.
Knead for 10 minutes, or until smooth and elastic. Place in a lightly oiled bowl, cover and leave to rise for one hour.
For the caramelised onions, heat the olive oil in a frying pan and add the onions and thyme. Cook for 25 minutes, or until soft and golden-brown.
Add the caster sugar and vinegar and cook for a further three minutes. Season with salt and pepper, set aside and clean the pan.
Return the pan to the heat, add the pancetta and rosemary and cook until crisp. Remove and set aside in a separate bowl.
Knock back the dough and then stretch out into a long oval shape.
Place on an oiled baking tray and cover for 30 minutes.
Make random dimples in the surface of the dough with your fingers. Top with the caramelised onions, a good drizzle of extra virgin olive oil and salt. Bake in the oven for 20 minutes, or until golden-brown.
Remove the tray and sprinkle with blue cheese, pancetta and rosemary. Bake for an extra two minutes or until the cheese begins to melt.
Dress with extra rosemary and serve immediately.