Put the olive oil, chopped garlic and crushed chilli into a large flameproof casserole and place over a medium heat.
As soon as it begins to sizzle add the tomatoes and 150 ml water then leave to simmer gently for 10 minutes until reduced and thickened.
Meanwhile put the vinegar and sugar into a small pan and boil until reduced to 1 tsp. Stir into the tomato sauce and keep hot.
Put another large pan over a high heat and when hot add the mussels, clams and white wine. Cover and cook for 2-3 minutes until the shellfish have just opened.
Tip the mussels, clams and all but the last tbsp or two ( which might be a bit gritty) of the cooking juices into the tomato sauce and stir together well.
Toast the slices of bread on both sides then singe over a naked gas flame for a slightly smoky taste. Rub one side of each slice with the peeled garlic clove.
Put the slices of toast into the base of four warmed bistro style plates or shallow soup bowls. Drizzle with a little olive oil.
Stir the parsley into the stew, then spoon it over the bread and serve immediately.