January 19, 2009
Mushrooms under glass were all the rage in the early 20th century. I first read about them in Mary McCarthy's novel The Group, in which a coterie of Vassar graduates trip through 1930s New York drinking cocktails called Clover Cup and Silver Fizz. Intrigued, I found them again (via google) in a 1918 novel by Mary Roberts Rinehart, memorably titled 'Twenty-Three and a Half Hours' Leave'. (The frontispiece of this novel is an image captioned with the words: 'In the elevator she said out of a clear sky: "You'll have to take that raincoat off, of course".') In Rinehart's book, a general eats his mushrooms under glass with broiled squab at "the best restaurant in the city".
The basic recipe is a circle of toasted bread topped with mushrooms, butter and cream. This assemblage is covered by a glass dish and cooked slowly in a low oven. 'How to Cook Vegetables' (1909), by the uncannily named Olive Green, offers four Mushrooms Under Glass recipes: with parsley butter and a little cream; with stems fried in salt, pepper and nutmeg; with nothing but fresh uncooked mushrooms; and with pre-sautéed mushrooms. 'The French Chef in Private American Families' (1922), by Xavier Raskin, recommends mushrooms of the Campestris variety, and suggests one large mushroom cap upended on the toast and stuffed with its stem, butter and cream.
I don't know when mushrooms under glass fell out of fashion. Maybe it had something to do with being able to reproduce a similar effect with aluminium foil, or even in a microwave. But the theatrical whimsy of the dish appealed to me, and I knew where I could buy some cheap glass butter dish covers.
I updated the recipe with goat cheese rather than cream and mixed thyme and lemon in with the butter. Make sure you use thick-cut bakery or homemade bread for the crouton base: thin, spongy supermarket bread won't hold up. You need to be very careful when cooking with glass because abrupt changes in temperature can cause it to shatter. Don't preheat your oven, and don't place the dishes too close to the heating element. When you remove the glass covers from the dish, don't place them on anything too hot or too cold.
The result is something like serving your guests very, very good mushrooms on toast. The mushroom flavour intensifies with the slow cooking, but the mushrooms remain shapely and firm. This means that very ordinary button or white mushrooms will work perfectly: the long cooking time gives their flavour a chance to shine. The herb butter and mushroom juices keep the bread moist in the oven, so it still tastes just-toasted when you bring it to the table. The best part is removing the glass cover in front of your guests: the aroma of mushrooms, previously trapped under the dish, rises suddenly with the steam. It's like an earthy, rich terrarium of yum.
An ebay search for bell jars, glass cloches and glass butter dish covers shows how expensive these things can be. These garden cloches from Smith & Hawkin would be dramatic piled high with mushrooms. Keep an eye out for glass covers in thrift stores - I bought mine at a local antique store for $2 each. Xavier Raskin offers this hint for those dealing with larger Private American Families: "If more convenient use one large bell oven glass, arranging all the mushrooms as above under the one bell glass."
Mushrooms Under Glass
12 medium-sized button/white mushrooms
4 tbsp unsalted butter, softened
1 tbsp freshly squeezed lemon juice
2 tsp fresh thyme leaves
salt and freshly ground black pepper
4 thick slices of bread
40g / 1.5oz firm goat cheese
Remove the stalks from the mushrooms. Chop stalks finely.
Using a fork, mash the thyme leaves, lemon juice and a little salt and pepper into the softened butter.
Cut out rounds of bread to the size of your glass cover. Toast bread. Spread one side with herb butter and place the bread, buttered side down, on a baking dish or plate. Spread more butter on top of the bread rounds. By this time you should have used about 3/4 of the butter.
Mix the chopped mushroom stalks in with the remainder of the butter, and then stuff each mushroom cap with these buttery stalks. Arrange 3 caps on each piece of toast. Crumble goat cheese over the mushrooms. Add salt and pepper generously.
Place glass covers over each round. Place the baking dishes/plates in the oven. Set the temperature to 200°F/100°C (do not pre-heat oven). Cook for 40 minutes. Serve immediately, removing glass covers at the table.