Heat the olive oil in a large pan on medium heat. Add the onions and salt and stir-fry for about ten minutes until the onions are golden and fragrant.
Reduce the heat and sauté for another 40 minutes, stirring occasionally until the onions are well browned.
In the meantime pre-heat the oven to 200°C. Butter a 23cm quiche dish and line with the pastry.
Bake blind for 10 minutes. Remove from the oven and allow to cool.
Reduce the oven temperature to 160°C.
After the onions have cooked for 40 minutes, add the balsamic vinegar and thyme leaves and sauté for another 10 minutes then remove from the heat.
Sprinkle 200ml of the grated cheddar cheese onto the crust. Spread the onions over the cheese and then top with the remaining 200ml cheese.
Whisk the milk, cream and eggs together and season with salt and pepper. Pour over the cheese and place in the oven.
Bake for 30 minutes.
Cool on a wire rack and serve with some grated parmesan (optional).
Reprinted with permission of Pink Polka Dot. To see more
recipes, click here.