Preheat the oven to 200ºC/gas 6, and insert a pizza stone or baking sheet to warm up.
Warm the milk. In a bowl, whisk the yeast and sugar with a splash of the milk, until it starts to foam.
In a separate bowl, mix the cornflour, flour, xanthan gum, egg and 4 teaspoons of olive oil with 1 teaspoon of sea salt and the remaining milk.
Add the yeast mixture, then use your hands to combine it all into a smooth dough.
In a cup, mix the bicarbonate of soda into the vinegar, then fold it into the dough. Place the dough in a lightly oiled bowl, cover with a damp tea towel and leave to prove in a warm place for 1 hour, until doubled in size.
Tip out the proved dough onto a lightly floured surface. Cut it into eight, then roll them out into circular pizza bases about 5mm thick.
To make the sauce, blanch the peas in boiling water for 3 minutes, then drain. Add them to a food processor, pick in the mint leaves, and add a lug of olive oil, season, then blitz to a paste.
In a bowl, combine the goat’s cheese (or curd) with half the lemon juice and half the zest.
Top each pizza with the pea purée. Grate and scatter over the courgette, then dollop on some of the goat’s cheese mixture.
Sprinkle polenta over the pizza stone or preheated tray, then place the pizzas on top. Bake in the oven for 10 to 12 minutes, or until cooked
and crispy at the edges.
Season them, and serve with some watercress, a drizzle of extra virgin olive oil and a grating of lemon zest.