Clean the onions, slice them thinly and put them in a small, heavy-bottomed saucepan. Add the sugar, 1 spoonful of olive oil, the white wine vinegar, the balsamic vinegar and salt according to taste (not too much). Stir well and put the pan over a low heat; then, as soon as the sugar begins to dissolve, turn the heat up. Stir frequently and when the onions become dense, almost caramelised, turn off the heat and put the pan to one side. Skin the sausages and sauté them in a heavy-bottomed frying pan with 2 spoonfuls of olive oil, breaking them up and stirring with a wooden spoon. Add the onions that you prepared previously, mix them together and cook for a few minutes. Toast the slices of bread on both sides and drizzle a little oil over each one. Divide the sausage and onion mixture – which is delicious – into 8 parts and distribute it on top of the bread...... buon appetito!