Place the sugar, oil and warm water into a bowl. Add the yeast and gently stir to dissolve the yeast.
Pour the flour into a bowl and make a well in the centre. Gradually add the yeast mixture to the flour, mixing it in with your hands until all the liquid is absorbed. It will be quite lumpy at this stage.
Knead the dough until smooth, then roll into a ball. Put some oil onto your hands and roll the ball around to cover it with oil.
Place the oiled ball of dough into a large floured dish. Cover with a cloth or some cling film and leave in a warm (but not hot) place to rise for one hour. The dough should have risen to three times its original size in this time.
While the dough is rising, make the topping. Preheat the oven to 180C/365F/Gas 4.
Place the whole garlic bulb into a sheet of kitchen foil and drizzle with olive oil. Wrap up the foil around the garlic to create a sealed package and place into the oven to roast for one hour, or until the garlic is cooked and tender.
Remove the garlic from the foil and allow to cool. Transfer to a bowl and add the butter and rosemary. Mash the garlic well and season with salt and freshly ground black pepper.
Rub a pizza pan or baking tray with olive oil.
Roll the dough into one large 2cm/1in thick rectangle. You may bake the loaf like this, or cut the dough into smaller pieces to make individual loaves.
Place the bread onto the oiled pan or tray and prick it all over with a fork.
Spread the roasted garlic and butter mixture over the dough, then leave to prove for 30 minutes.
Preheat the oven to 230C/445F/Gas 8.
Transfer the dough to the oven and bake for 15-20 minutes, or until golden-brown and risen.