Adapted from Nigel Slater's Tender. I've replaced some of the cream with milk; I've also reduced the amount of cheese. On mushrooms: for a weightier dinner, try adding a couple of fleshy portobellos. —Nicholas Day
Preheat the oven to 350 degrees. Cut the mushrooms into bite-size pieces. Warm a tablespoon of butter and two tablespoons olive oil in a saucepan, then add the mushrooms. Stirring occasionally, saute the mushrooms until some of their liquid cooks away and they start to brown. Add the white wine and boil for a couple of minutes. Then add the cream and milk and let simmer for several more minutes. Turn off the heat. (If you have time, leave this to steep; the cream and milk will get wonderfully mushroomy.)
Wash the spinach well and put in a saucepan over medium heat. Cover the pan and let the spinach steam for several minutes. Then drain it and squeeze the water out.
Add the spinach and a couple tablespoons of parmesan to the mushroom-cream mixture. Season with salt and pepper and transfer to a shallow baking dish. Sprinkle the remaining parmesan on top. Cook for about a half-hour, or until golden. (If the cheese melts but does not crisp, run it under the broiler for several minutes.)