Preheat your oven to 200c fan/220c conventional/Gas mark 6.
Start by preparing the vegetables, cut the tops and bottom off each onion, remove the outmost later of skin, but leave on as much as you can, then cut in half, and each half into quarters. Cut the leeks, carrots and celery into 2cm chunks (you can leave the carrots unpeeled). Cut the top off of the garlic bulb.
Put all of your vegetables on to a baking tray, drizzle with the olive oil, and a good seasoning of salt and pepper.
Put into the oven and set a timer for 50 minutes.
When the timer goes off remove the tray from the oven give everything a good shake and add in tomato puree and fresh thyme. Return to the oven for 10 minutes.
When the vegetables have finished cooking and have turned very brown, put them into a large saucepan, carefully squeeze the garlic out of its skin in to the vegetables, add in the bay leaves, stock cubes, water and white wine. Bring to the boil, and simmer for 1 hour (it should be bubbling).
Strain the mixture into a large bowl, discarding the vegetables. Pour the gravy back into the saucepan.
Put the cornflour into a small dish and add just enough of the gravy to make a smooth paste. Now pour the paste back into the saucepan of gravy (we use this method to avoid flour lumps). Mix well. Add in soy sauce and redcurrant jelly.
Cook over a low heat for a further 5-10 minutes until thickened, whisking often to avoid any lumps.