Dry fry the mince, half the onion and all mushrooms until browned. Add yeast extract and stir in thyme. Add about 100ml water or stock if mix is too thick.
Grease a shallow dish and lay half the potatoes and the remaining onions in. Add half of the mince mix, half of the cheese. Layer on the rest of mince, making sure to spread out evenly. Put the rest of the potatoes on top. Cover with lid or foil.
Bake until the potatoes are tender, about 1 1/2 hours. Uncover, top with remaining cheese and put under grill until cheese is melted and browned.
If I am making this for children, I cut the yeast extract down as the taste can be a bit strong.
Wow this is sooo tasty. Got a bit confused about wether to add all mushrooms or half with mince but it turned out right in the end. Kids loved it, so did my parents. tried with lamb mince too. Super!! - 12 Jul 2012