For the cauliflower and corn bake: preheat the oven to 180°C, fan 160°C, gas 4. Bring a large saucepan of water to the boil, add the cauliflower and cook for 5 minutes, drain and tip into a 1-litre ovenproof dish. Make up 250ml vegetable stock using the bouillon powder. Place the milk in a saucepan with the vegetable stock and heat gently. In a cup, mix the cornflour with a few tablespoons of the milk mixture to make a smooth paste, then pour into the pan along with half the sweetcorn and the mustard and bring to the boil, stirring all the time, until thickened. Pour into a food processor or blender and whiz to make a smooth sauce. Stir in the remaining sweetcorn and the peas. Pour the sauce mixture over the cauliflower and sprinkle the top with the breadcrumbs and cheese. Bake for 15 minutes until the topping is golden and crusty.
For the slow-roasted tomatoes: preheat the oven to 120°C, fan 100°C, gas ½. Place the tomatoes in a large bowl and toss well with the oil, vinegar and thyme. Spread out on a baking tray, cut side up, and bake slowly for 2 hours until they have shrunk and shrivelled a little. Leave to cool. To serve, scatter with the basil.