Reproduced (in a slightly abbreviated form) from Bread Matters – How and Why to Make Your Own with kind permission from Andrew Whitley. Notes in square brackets are my own.
Step 1: make the sponge
Fresh Yeast – 3g [a teaspoon of dried yeast will also work]
Water (at 20C) – 150g
Strong White Flour or Italian Type 0 Flour – 75g
Stoneground wholemeal flour – 75g
Total – 303g
Dissolve the yeast in the water, add the flours and mix to a soft sponge. [This means give it a really quick mix (a few seconds) and don't worry too much about lumps, in the UK I assume 20C to be about normal room temperature]. Cover and ferment the sponge for 18-48 hours [I leave in a bowl covered with a plate at room temperature].
Step 2: make the basic dough
Sponge from Step 1.
Semolina Flour – 270g
Sea Salt – 4g
Water – 135g
Mix the ingredients. A dough temperature of 27C is ideal – use some warm water if the dough has been in a cool place*. Knead until stretchy and silky, adding a little more water if the dough is hard to stretch and tears easily. Cover and allow to rise for one-two hours.
* Andrew’s book covers this in more detail and gives a formula for calculating how hot the water needs to be.
Proceed to Step 3 or…
…If you are making the plain loaf, mould into a fat rugby ball shape, dip into a bowl of semolina flour to cover it and place the loaf on a lined baking tray with plenty of semolina. Allow to rise for at least one hour. Then, using a sharp knife, make two cuts following the contours of the loaf. Place in a very hot oven (pre-heated to 230-240C) for about 30 minutes, dropping the oven temperature by 20C after 10 minutes or so.
Step 3: make the Semolina, Raisin and Fennel Bannock
Soaked Raisin Mix
Raisins – 220g
Fennel seeds – 20g
Water (hot), fruit juice, or spirit – 70g
Place the raisins and fennel seeds in a polythene bag, seal and soak overnight or longer (this can be done while the sponge is fermenting in Step 1).
Altamura Dough from Step 2 – 540g
Soaked Raisin Mix – 300g
Drain any excess liquid from the soaked raisins and fennel seeds. Gently fold them into the aerated dough, taking care not to knock all the air out of the dough. Mould up gently and not very tightly into a round cob. If a lot of raisins are sticking out of the top surface of the load, pick them off and push them into the base – prominent fruits always get burnt and go bitter. Dip the moulded cob into semolina flour and place it on a baking tray that has been lightly dusted with semolina. Cover the tray loosely and put it in a warm place to prove.
The dough is soft and weighed down with raisins so this cob will flow out into a flattish bannock as it proves. When it is ready, bake it in a moderate over (about 190C) for 30-40 minutes. Leave it until it is completely cool before attempting to cut it.