Instructions: Preheat the oven to 180C/350F/gas 4. Remove the onion skin, cut in half lengthways and remove the root. Place the tatin pan over heat and add the butter. Once melted add the sugar and the thyme leaves.

Arrange the onions in the pan (cut side down) until the pan base is full.

Slice the amount of onions you may need to fill in any gaps.

Season with salt and pepper and drizzle over the vinegar. Turn down heat and let the onions cook gently for around 10 minutes. Cover the pan with foil, then place into the oven for 30 minutes.

Roll out the puff pastry and cut out 2 discs the same diameter as the tatin pan. Brush the sides of the pastry with egg wash, then spread the grated cheese on one of the pastry discs evenly. Place the other pastry disc on top to form a sandwich. Carefully seal down the sides of the disc and leave to rest for 20 minutes. Remove the onions from the oven, together with the foil lid. Carefully place the pastry sandwich over the top of the onions, taking care not to burn yourself.

Return the tatin to the oven and cook for an additional 20 minutes or until the pastry is crisp and golden. Leave the tatin to cool for 15 minutes before attempting to turn out.

Serve with a little herb salad and herb oil, parmesan shavings and a sprig of thyme.

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