Preheat the oven to 220C/200C Fan/Gas 7. Line a large baking sheet with baking paper.
Put the almonds, grated swede, egg, Parmesan, oil and a good pinch of salt in a large bowl and mix thoroughly to make a slightly sticky dough. (If the dough is very sticky, add extra almonds or Parmesan cheese to the mixture.)
Put the dough on the prepared baking sheet, cover with another piece of baking paper and roll with a rolling pin, or pat the dough firmly with your hands until it’s about 23cm/9in in diameter. Remove the top piece of baking paper, drizzle with a little oil and bake for 10 minutes, or until firm and lightly browned around the edges.
While the dough is cooking, place the tomatoes, garlic, tomato purée and basil leaves in a food processor and blitz until well combined but not completely smooth. Season with a little salt and pepper.
For the topping, fry the pancetta and mushrooms together in a medium frying pan for about 5 minutes, or until lightly browned, adding a splash of oil if needed.
Take the pizza base out of the oven and spread with the tomato sauce. Scatter over the pancetta and mushrooms and sprinkle with the Parmesan. Season with ground black pepper, drizzle with a little oil and bake for a further 1–2 minutes, or until the cheese has melted. Scatter a few more basil leaves over the top, drizzle with oil and serve.