Cut the onions in half-length ways and finely slice place in a medium sized non-stick saucepan with the balsamic and Lyles golden syrup. Allow to cook down on a medium to low heat for approximately 20-25 mins with the lid on. The onions are ready when they are soft but have some texture remaining.

Line two sets of mini muffin tins with the filo pastry that has been brushed with butter and cut into 70x70mm squares, use 3 squares for each round tin, arranging at different angles to create points with the pastry around each tin hole.

Bake the pastry for 8-10 mins at 200C Gas mark 6 or until a rich golden brown colour.

When the cases have cooled fill with the caramelized onion mix and sprinkle each one with crumbled feta.