Simply double (or even triple) the quantities if you have a large gang of trick-or-treaters to feed.
Preheat the oven to gas 7, 220°C, fan 200°C. Put the passata and olive oil in a pan and bring to the boil. Reduce the heat and simmer for 5 minutes, or until thickened.
Empty the pizza base mix into a bowl and stir in 100ml (3 1/2fl oz) warm water. Mix to a soft dough, then tip out onto a lightly floured surface and knead for 5 minutes, or until smooth. Roll out the dough to roughly 24cm (9 1/2in) in diameter. Transfer to a large, greased baking sheet and turn up the edge of the base for a crust. Leave to stand in a warm place for 10 minutes.
Meanwhile, thinly slice 8 olive halves lenthways into 4 to make 32 legs for the spider (each spider has eight). Dice two more olive halves to make eyes for the mozzarella ghosts.
Spread the passata over the base, allowing a 1cm (1/2in) border. Top
with the salami and arrange the torn mozzarella in ghost shapes (with room to spread). Position the remaining olives, cut-side down, and arrange 4 spidery legs on either side.
Cook the pizza for 15-18 minutes, until bubbling and golden. Remove from the oven and leave to cool for
1 minute, before adding the reserved olive eyes to each melted mozzarella ghost. Serve immediately.
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