This dish would be a great vegetarian Christmas dinner option - the rich mushrooms are perfect with gravy, and since gruyère is a little more expensive than a lot of cheeses, it feels a bit special and worthy of your Christmas plate. It's just the thing to have pride of place in the middle of the table, so everyone can go back for an extra slice whenever they fancy (probably every few minutes, considering how tasty this was!).
Perhaps my favourite thing about this tart is that it's just as nice cold as it is warm, so if any slices manage to escape the Christmas dinner table uneaten, they'll make a great lunch the next day with salad and coleslaw, and perhaps a slice of bread. I didn't bother to reheat mine, and it was still absolutely delicious - in fact, if anything the flavours are even stronger when the tart is cold.
Putting together this tart is really easy - I used shop-bought shortcrust pastry, so all I needed to do was to roll it out nice and thin, and then blind bake it for twenty minutes or so while I prepared the filling ingredients. Of course you could make your own pastry if you prefer, but I see no shame in using some shop-bought ingredients every now and then.
The first layer of the tart is my secret ingredient - a layer of mushroom pâté. This helps the tart to stay nice and fluffy, as well as ensuring that the rich mushroom flavour is present throughout its whole depth. The pâté is then covered with a thin layer of egg, fresh parsley, sautéed mushrooms, and finally the gruyère cheese, which provides a nice melty topping.
I'll definitely be making this mushroom and gruyère tart again next Christmas - it's easy to put together, and its versatility means that it can be served for lunch, dinner - or even your main Christmas feast.