Heat a large saucepan over a medium-high heat until hot.
Discard any mussels that don't close when tapped on their shells. Add the mussels and then the wine to the saucepan and cover, allowing the steam to cook the mussels. Shake the pan a few times during cooking.
Drain the mussels after 3-4 minutes and discard any that haven't opened. Use a small fork to remove the mussels from the shells; transfer to a small bowl and reserve to one side.
Meanwhile, prepare the tomato sauce by heating the olive oil in a large saucepan over a medium-high heat. Add the garlic and stir well, cooking for 1 minute then add the mushrooms and cook for a further 2 minutes. Add the chopped tomatoes to the saucepan and bring to a simmer. Stir in the sugar and season with salt and pepper. Simmer for 4-5 minutes, stirring occasionally until the sauce has thickened, then remove from the heat and reserve to one side.
Bring a large saucepan of salted water to the boil and cook the spaghetti until 'al dente'; usually 8-10 minutes. Reheat the tomato sauce and stir the mussels into it to warm through. Drain the spaghetti and toss with the sauce.
Season to taste and spoon onto serving plates. Drizzle with the extra-virgin olive oil and serve immediately.