Make the pizza dough: put the bread mix in a large bowl, pour over ½ tbsp olive oil and 175ml lukewarm water. Stir until a dough is formed, then tip out onto a lightly floured surface and knead for 5-10 mins until smooth. Rub the bowl with a little oil, pop in the dough, cover with cling film and leave to rise in a warm place for 45 mins or until doubled in size.
Meanwhile, make the pizza topping. Heat 1/2 tbsp oil in a large frying pan over a medium heat. Add the bacon and cook until just starting to crisp. Remove with a slotted spoon and drain on kitchen paper. Add another drizzle of oil to the pan, then tip in the sprouts, season and cook for 3-4 mins until softened and starting to caramelise around the edges. Set aside.
For the white sauce, melt the butter in a small pan, add the garlic and let it sizzle gently for 30 secs. Pour in the cream, grate over some nutmeg, season and simmer for 5 mins until thickened and reduced.
Heat oven to 220C/200C fan/gas 7 and pop in 2 large trays. Carefully remove the dough from the bowl and, without punching out all the air, divide into 4. Using your hands or a rolling pin, shape each quarter into a rough circle 18-20cm in diameter. Transfer to the hot trays and cook for 4 mins. Remove from the oven, spread over the white sauce, then scatter with the sprouts, bacon and Stilton. Toss the sage leaves with the remaining oil and divide among the pizzas. Cook for 5-10 mins until the dough is golden brown and the top is bubbling. Grind over some black pepper before serving.