Preheat the oven to 200C/400F/Gas 6.
Blend the flour, baking powder, basil and butter in a food processor bowl until the mixture resembles breadcrumbs.
Crack the egg into the food processor bowl and pour in two tablespoons of the milk. Pulse, adding another tablespoon of milk if necessary to form a dough.
Turn the mixture out onto a lightly floured surface and knead until smooth and elastic. Roll the dough out into a thick round using a floured rolling pin.
Press the tomatoes and chickpeas into the surface of the dough and place onto a baking sheet.
Drizzle the olive oil over the tomatoes and chorizo and season well with salt and freshly ground black pepper.
Bake the dough in the oven for 10-12 minutes, or until golden-brown and slightly risen.
