A quick note: you'd assume, if you'd not eaten Flammkuchen before, you might assume that one 'pizza' per person might be enough. Well - you'd be wrong. It's very more-ish, and the thinness of the base makes it feel virtuous enough that you could easily have a second. And a third.
2 cups flour
2 1/2 tablespoons oil
2/3 cup water
Pinch of salt
500ml milk with 1 tablespoon lemon vinegar
or 1/2 to 1 cup ricotta
250ml milk with 1 tablespoon lemon vinegar
or 1/2 to 1 cup sour cream
1 clove garlic
1 large onion
10 rashers bacon
Mix the dough ingredients together. Divide into two and roll each out as thinly and widely as possible to make the Flammkuchen base. (Make sure it'll still fit in your oven.) Oil two baking sheets and place one under each base.
Prepare the buttermilk/sour-cream-substitute by mixing the 250ml milk with 1 tablespoon of lemon vinegar, stirring, and allowing to curdle.
Make the ricotta by mixing 500ml milk with 1 tablespoon of lemon vinegar in a pan and setting on a low heat. Stir occasionally.
After a few minutes, the curds will start to pull away from the side of the pan like this.
Within ten minutes the milk will look like this. Prepare a colander by lining it with folded cheesecloth (or an old tablerunner folded in four, like me) and pour the mixture through. Allow to sit for five minutes before using the ricotta.
Finely chop the garlic and mix with the ricotta and buttermilk, in a blender if you want to make it really smooth. Season and spread half of the mixture on to each pastry base.
Cut the onion in half, and finely slice each half into crescent moons. Put in a heavily oiled pan and let them soften over a low heat. Chop the ten rashers of bacon into thin matchsticks and add to the onion pan until they are semi-cooked, and the onions are caramelizing a little.
Spread half of the onion and bacon mixture on to each Flammkuche and bake on the middle shelf of the oven at 220 degrees (430 Fahrenheit) for fifteen minutes, turning halfway if necessary.
It's ready once the toppings are slightly browned. Serve, and eat with a knife and fork unless you feel like you can balance that paper-thin crust on your fingers.