Preheat oven to 180˚C. Cut mushrooms into smaller pieces if necessary and then place into the bowl of a food processor. Process in batches until finely chopped.
In a large frying pan (or oven safe cast iron/ buffet casserole) heat a drizzle of olive oil. Fry mushrooms until completely dry and turning golden brown. Fry in batches if necessary. Set a side in a bowl.
To the same pan add the beef mince and fry until beginning to brown. Add the onion, garlic, curry powder and turmeric. Cook until tender and fragrant.
Add the cooked mushrooms back into the mince mixture. Add in vinegar, worcestershire sauce, chutney and raisins. Adjust seasoning. Level out filling in oven safe dish or transfer to an oven safe dish.
Whisk together topping ingredients and season. Gently pour egg custard onto the top of the mushroom and mince filling. Scatter with bay leaves and bake for 45-60 minutes until set and deeply golden brown.
Serve bobotie with sambals and yellow rice.