Pour the olive oil into a deep pan and place over a medium heat.
Add the garlic and cook till golden brown.
Add the onion and salt and cook till the onion is translucent, golden brown and soft.
Add the tomato purée and cook into the onion for a few minutes.
Pour in the cream of tomato soup and add the Worcestershire sauce, Marmite, ground cumin and chilli flakes, mix through and leave to simmer till the Marmite has melted away.
Crumble in the lamb mince and stir, breaking up the meat while it cooks in the sauce to prevent any huge clumps of mince.
Pour in the milk and simmer for about 30 minutes till the sauce has thickened and really coated the meat.
Add the gravy granules, stir and let the granules dissolve.
Leave on the lowest heat, covered with a lid, for 10 minutes and then take off the heat.
To serve, cut open the baps and toast them on both sides under the grill or in a toaster.
To each one add a generous helping of the mince, sprinkle on the pickled egg and red onion, top with a bap.
