Heat the oil in a heavy saucepan and sauté the vegetables, not the apple, for 6-7 minutes or until light golden brown. Add the apple and cook for 2 minutes.
Pour the red wine and apple juice into the pan and scrape up any sediment from the bottom using a wooden spoon. Bring to the boil and simmer until reduced by half.
Add the lamb jus, garlic and thyme. Bring to a slow simmer and cook for 20 minutes. Pass through a fine sieve, season to taste and, if the mixture is a little bitter, add some sugar.
Leave to cool, partially covered by plastic film to ensure the steam escapes. Once cool, cover tightly and place in the fridge for up to 1 week. The jus will set and needs to be brought back to warm room temperature to serve.