Place the pumpkin in a roasting tin, cut side down. Fill the roasting tin with about 1cm of water.
Roast the pumpkin in the preheated oven until tender; approximately 30 to 45 minutes. Add more water to the tin if necessary while roasting.
Meanwhile caramelise the onions: In a small frying pan heat the olive oil over medium heat. Add the sliced onions and stir only occasionally. After stirring every few minutes or so add a teaspoon of water as needed to release the caramelised bits from the bottom of the frying pan. Continue this process until the onions are soft and caramelised; about 20 minutes.
Meanwhile toast the pine nuts by heating them in a dry frying pan over medium heat. Watch carefully and stir occasionally for about 5 minutes or until the pine nuts are golden brown.
Once the pumpkin is slightly cool remove the skin and dice into 3cm pieces.
Assemble the salad by combining the diced pumpkin, caramelised onions, toasted pine nuts, feta, mint, salt and pepper in a mixing bowl. Toss the salad to combine all ingredients then place in a serving bowl or platter. Drizzle with olive oil and balsamic vinegar to serve.