Heat your oven to 200°C/Fan 180°C/Gas 6. Tip half the saffron powder into a small bowl or cup. Mix with 2 tbsp olive oil. Season. Pop to one side.
Warm a large, dry pan on the hob. Tip in the lardons and fry in the dry pan for about 8 mins till they are crisp and the fat has run (if they seem dry, add a splash of oil while they cook). Use a slotted spoon to lift them out. Pop on a plate lined with kitchen paper.
Trim and rinse the leeks. Finely slice them. Peel and grate or crush the garlic. Add the leeks to the pan. Fry in the fat from the lardons for 4-5 mins till soft. Fill the kettle and boil it.
Add the garlic, the risotto rice and the rest of the saffron powder to the leeks. Cook and stir for 1 min. Pour 700ml hot water from the kettle into another pan. Crumble in the stock cube. Keep warm over a low heat.
Gradually add the stock to the risotto rice, a ladleful at a time. Cook over a low heat till each ladleful of stock has been absorbed before adding more. The rice should be tender but still have a bit of a bite.
While the risotto is cooking, break the cauliflower into florets. Drizzle with the saffron oil. Roast in the oven for 15-20 mins till tender and charred at the edges.
Grate the Parmesan. Rinse the spinach. When the risotto is almost ready, stir in the spinach, half the Parmesan and most of the lardons.
Serve the risotto topped with the rest of the lardons, the roast cauliflower and the remaining Parmesan for sprinkling.