Preheat the oven to 180°C.

Place the sheet of chilled pastry on a floured surface. Using a plate or tart tin, cut a circle with the widest diameter possible depending on the width of the pastry. (Do not roll it out). Score a border of 1-1½ cm wide around the edge of the pastry and prick the inner circle all over with a fork to prevent the centre from rising during baking. Place on a lined or greased baking tray and refrigerate until needed.

Halve and peel the onions, keeping the root section intact. Slice each half of the onions through the root section into 4 wedges. Place on a baking tray, drizzle with Olive Oil and sprinkle with sugar. Season with a generous grinding of One for All, salt and pepper.

Place in the preheated oven for 20 minutes or until lightly caramelized and slightly blackened on the edges. Remove from the oven and leave to rest until cool enough to handle. Increase the oven temperature to 200°C.

Fill the centre of the tart base with onion wedges, overlapping and interspersed with chunks or slices of taleggio. Season with a few more grindings of One for All or fresh thyme and drizzle with Olive Oil. Make an egg wash by whisking the egg with the milk and brush the border of the tart. Do not allow the egg wash to run down the sides of the tart base, as this will act like glue, preventing the pastry from puffing up nicely.

Bake in a very hot oven for 20 minutes or until beautifully puffed up and golden brown.

Serve immediately drizzled with Extra Virgin Olive Oil and aged Noble vinegar. Delicious with roast chicken or a simple green salad.

Tips:
– Noble Tonic 05:XO is a blend of Canadian maple syrup, Sherry Vinegar and single grain Bourbon which has been aged for 5 years in charred oak barrels. If you can’t get your hands on this, you can make your own quick fix by placing ½ cup sherry or balsamic vinegar in a saucepan, add 60ml maple syrup and a splash of Bourbon and simmer until reduced by half or until thick and syrupy.
– If you can’t find taleggio cheese, you can try asiago or alternatively young brie or camembert.