Add the dough ingredients except the bicarbonate of soda, and knead well for 10 minutes.
Cover the bowl with a shower hat and leave on the counter for 4 hours.
Scrape the dough out onto a floury surface and sprinkle over the bicarb. Do this through a sieve as it has a tendency to ball up and you really want it well distributed.
Gently knead the dough just to incorporate the bicarb. Move the dough aside.
Scatter some coarse corn meal or semolina on the counter and place the dough on top. Flour the top with a bit of flour and roll the dough out to about 2 cm in thickness. Using an 8 cm (or so) cutter with straight sides, cut out the muffins.
Line a baking try with semolina and place the muffins on the baking tray.
Cover them with plastic and let them rest for 2-3 hours or until they pass the probe test.
Preheat the oven to 220 degrees C. Sprinkle semolina on the tops of all the muffins and place a second baking tray right side up and on top of the muffins. This will keep them flat as they cook, and brown their little tops!!
Pop them in the oven and bake them for 15-20 minutes. Check them after 15 minutes to make sure the tops are not getting too brown. If so, remove the tray and cover the tops with some parchment paper. Once they are flat, they are flat! The will not dome.
Remove them from the oven and let them cool completely on a wire rack.