Place the porcini in a small bowl and pour 350ml (12fl oz) of the hot water over them. Put the sun-dried tomatoes in a separate small bowl and pour the remaining hot water over them. Allow to soak for about 20 minutes or until softened.
Scoop the mushrooms out of their soaking liquid and finely chop them. Strain the soaking liquid through a fine-mesh sieve into a bowl. Strain the sun-dried tomato soaking liquid into the same bowl and set aside. Coarsely chop the tomatoes.
Preheat the oven to 180°C (350°F, gas mark 4). Heat the olive oil and 3 tablespoons of the mushroom and tomato soaking liquid in a medium saucepan over medium heat. Add the onion and garlic to the pan and cook for about 7 minutes or until the onion is golden.
Add the rice, stirring to coat. Add the mushrooms and tomatoes, the remaining soaking liquid, sage and pepper, and bring to the boil. Transfer the rice mixture to a 20cm (8in) square baking dish. Cover with foil, transfer to the oven and bake for about 40 minutes or until the rice is tender and all the liquid has been absorbed. Sprinkle the hot rice with the Cheddar and Parmesan cheeses before serving.
Parmesan cheese is not truly vegetarian, as it contains animal rennet. To make this dish 100% vegetarian, omit the cheese or find a suitable vegetarian substitute made without animal rennet. In supermarkets look for the 'parmesan style hard cheeses' which are suitable for vegetarians.
Some more ideas
*You can make this dish with other dried mushrooms, such as Chinese black mushrooms. Or use sliced fresh chestnut mushrooms and replace the mushroom soaking water with low-sodium vegetable stock in step 4. *To vary the flavour, try other reduced-fat firm or hard cheeses suitable for grating.
*The concentrated flavour of dried porcini and sun-dried tomatoes enriches this dish without adding any fat, sugar or salt. These wonderful taste enhancers can be kept in your storecupboard for a long time. *Brown rice is a particularly good grain for blood pressure. It is rich in magnesium, folate and other nutrients, as well as insoluble fibre. Many of these nutrients get stripped out in the milling process that is used to produce white rice.