For the quick pickle combine all ingredients in a bowl. Set aside for 20 minutes stirring occasionally then drain. Heat 1 tablespoon of oil in a pan over a medium heat. Cook the mushrooms for 5 minutes then drain onto a paper towel.
In a food processor blend mushrooms, lemongrass, coriander, shallot and garlic until smooth.
Roll pork mince into 16 balls. Heat 1 tablespoon of oil in a large non stick frying pan over a medium heat. Cook for 10 minutes, turning often until brown and cooked through. set aside on a plate lined with a paper towel to drain.
Split the bread rolls length ways, cutting part way through. Generously spread both sides with mayo and hoisin sauce. Divide carrot and cucumber between the rolls and top with the meatballs, coriander and chilli.