This is -- you know spanakopita? This is like that, only with mushrooms and lamb instead of spinach.
The day before, for dinner, have slow roasted lamb with lemon and thyme and oregano, with rice. Keep the leftovers.
Then you want some filo. (Phyllo.) If you are aethereal_girl you could make some, but it's very easily available in packets. You want eight sheets about 8 inches square each. And you need an oven dish that size.
Put some of the lamb fat from the leftover lamb in a frying pan and saute an onion, a garlic clove and four large portabello mushrooms in it, with some thyme and black pepper. Stir from time to time. Turn it off when it's done.
Meanwhile, beat two eggs and the amount of ricotta you want for spanakopita in a bowl. That's maybe two ounces? Beat it well so that the ricotta is in small bits.
Cut up the cold lamb, removing fat, and put it in the bowl with the eggs and ricotta. This would be maybe a quarter of a pound of lamb at the most, and you want it in small bite sized pieces, not shreds.
(You will also have some lamb bones and jelly. You can therefore make cawl, put them in a big pot with water, onions, garlic, a leek, parsnips, carrots and potatoes, and pearl barley if you like it. Bring to the boil and then simmer for an hour.)
Put the oven to pre-heat to 180C.
Take some leftover rice and grains -- look, you started with a cup of rice and grains, and you cooked it in the rice cooker and then at dinner yesterday three people ate what they wanted, and this is what was left. So maybe a quarter of a cup of cold cooked mixed basmati rice, sprouted brown rice and whatever. Put this in the bowl with the lamb and eggs and ricotta, and mix it all up.
Then take the frying pan with the sauted onions and mushrooms and stuff, which should be all soft and sauted glop by now. Pour it into the other stuff in the bowl and stir. It'll go all grey and horrible looking, but be resolute.
Carefully place four slices of filo on the bottom of the oven dish. Then pour all of the filling on, and flatten it down a bit. Put the other four slices of filo over the top, and dot with butter. People tell you to melt butter and put it between the sheets but really this is all you need to do.
Bake for 30 minutes at 180C. Surprisingly good hot or cold.