Mix together the blueberries, sugar, cornflour, cinnamon and lemon juice in a large bowl. Set aside.
Divide the pastry in half and shape each half into a ball. Roll one half out on a floured surface into a large circle about 3mm/1/8in thick. Carefully lift it into a 9 inch pie dish and press into the edges, trim off the excess pastry, leaving a couple of cm overhanging.
Sprinkle over the tablespoon of semolina then tip in the blueberry filling and spread level. Set aside.
Roll the other ball of pastry out as above and use a pizza wheel or sharp knife to cut it into 1-2 inch wide strips.
Using your two longest strips, lay on the tart to make a cross in the centre – don’t attach the strips to the edges. The strip that’s vertical as you look at it should be on top.
Lay two strips of pastry horizontally, either side of the horizontal strip.
Fold the middle horizontal strip back on itself to the left and put a vertical strip on the tart to the right of the folded back strip. Unfold the pastry strip back to its original position, then repeat on the other side.
Now repeat with the vertical strips: fold up the middle vertical strip, put a horizontal strip at the bottom, then fold back the middle strip. Repeat this process on all sides until the pie is covered.
Press all the edges down to seal (use a drop of water to help them stick if needed) then trim off the excess and either crimp the edges or press with a fork.
*See post above for photo instructions for making a lattice and for making pastry braids.
Pop the pie in the fridge for 20-30 minutes while you preheat the oven to 200C/400F/gas mark 6.
Brush the top of the pie with soy milk and sprinkle with granulated sugar. Bake for 20 minutes then turn the oven down to 180C/350F/gas mark 4 and bake for a further 30-40 minutes until the filling is bubbling and the crust is golden. If the crust starts to darken too much before the pie is done then loosely cover it with tin foil partway through baking.
Allow the pie to cool for at least 3 hours at room temperature before serving. Store any leftovers in the refrigerator for up to 5 days.