1. Heat the milk until just warm to the touch. Pour the milk into a bowl and dissolve the yeast in it.
2. Add the sesame seeds, salt and 2 types of flour (reserve some of the flour for later). Beat all the ingredients for the dough with a large spoon. Let the dough rise, covered, for approx. 30 min.
3. Preheat a baking sheet in the oven. Tip the dough out onto a floured surface and knead thoroughly.
4. Divide the dough into 2 portions and roll each one into a rectangle (approx. 12 x 15 in) – make sure there is plenty of flour on the worktop.
5. Cut the dough into 24 squares (approx. 4 x 4 in). Place the squares on sheets of baking parchment and prick with a fork.
6. Slide the baking parchment onto the hot baking sheet, and bake – one tray at a time – on the highest shelf. Bake at 430°F for about 5 min., then turn the crispbread over and finish baking.