Heat oil in a large saucepan, add onion, garlic and mushrooms. Cook for 2-3 minutes, stirring continuously.
Add rice and stock, bring to the boil. Reduce heat to a simmer, cover and continue to cook for 12-14 minutes, stirring occasionally, until liquid is absorbed and rice is tender. Remove from heat and stir in parmesan cheese.
Meanwhile, cut tops off capsicums and keep intact. Scoop out seeds and membrane and discard. Lightly brush the skin of each capsicum with extra oil. Spoon rice mixture into capsicums and replace tops. Place into a greased baking dish large enough to fit the capsicums.
Combine boiling water and Leggo’s Sugo. Pour carefully into base of dish around capsicums. Cover with greased aluminium foil and bake in a preheated oven at 180°C for 30 minutes. Remove foil and bake a further 30 minutes. Spoon a little of the sauce onto serving plates and place a capsicum in the centre.